Nita - Pulse

If you don't have Nita - Pulse yet but want to try her out, she is available as a Trial Operative in Story Missions SP5-7 and SP5-8 (Main Story // Journey // Philossia / Abyssal Dawn)
Pulse is also available as a Trial Operative in Story Missions SP6-6 and SP6-7 (Main Story // Journey // Philossia / Defiant Bloom).

Pulse provides high damage with good survivability, however she has almost no mobility which can make her vulnerable and makes her ineffective against mobile enemies.
Nita making you do a minigame for the entirety of combat means that your situational awareness can be very low when playing Nita, although Nita does have very high self-healing, which means her overall survivability can be great.. or terrible, since her ult hurts her.
All of Nita's damage scaling entirely off of her HP and not ATK means that she doesn't work perfectly with most of the common support buffs, which typically buff ATK.

Note that if you don't have any of her survivability or healing Neuronics/Auctus Drives, then Pulse can kill herself if she's played improperly.

As an Auctus Drive operative, Pulse was freely available with her 5* weapon at T2 with a logistics squad during her initial release.
Many players will thus have her mostly-maxed already.

The Basics

Role: Main DPS
Deals Thermal Damage
Weapon Type: Shotgun
Deals entirely skill damage
Mobility is horrendous
Can heal herself extremely well

How to use Nita - Pulse

Use Nita's ult, which deals damage and causes Pulse to lose HP
Use Nita's standard skill two times
Each standard skill use performs 6 consecutive punches that also restore HP
For each punch - Just click whilst in the blue region

Repeat

If she doesn't have max investment, then Pulse might need up to 4 Standard Skill casts in order to get back to max HP after using her ult.

How to build Nita - Pulse

Weapon: Timeless Rhythm
Weapon Parts: Max HP
Logistics Squad: Sorbus
+10.0% Max HP
+106 Alignment Index
+8.5% Thermal Damage
Best teammates:
Vidya - Celestial Swan
Siris - Freefin

Specifics:

Ultimate Skill

Nita removes 99% of her HP, and does a huge punch in front of her to deal massive Thermal damage.

With its first Neuronic, 60% of the consumed HP is converted to a shield.
Given that Nita will have basically no HP after using her ult, this Neuronic is extremely important for her survivability.

Nita's ult has a U-Energy cost of 0 and a low cooldown of 20s (which can be reduced by her standard skill even more), which makes this theoretically very spammable.
In practice though, since the damage of this skill is entirely determined by Nita's HP when it is used, you'll want Nita to be fully healed before she uses it.
How often Nita can use her ult is thus entirely determined by how quickly she can heal herself back to full HP using her standard skill.

Standard Skill

Nita enter a special "Bhairava" state where she does a combo of punches in front of her.
Nita does five punches followed by a larger sixth punch that deals much higher damage.
Each punch restores some U-Energy.

For each punch, there will be what is basically a minigame for you to do, where you have to use her standard skill again whilst the bar is in the perfect blue region.
This is pretty intuitive and the timing is consistent, but does require a little practice to be able to get it perfect every time.
If it isn't in the perfect blue region, the punch will deal half damage.

For each punch, Nita gains "Cinder Chimes".
If Nita gains too many Cinder Chimes she'll lose 10% of her Max HP and exit the state.
Nita gains 1 Cinder Chime for a perfect punch, and 4 for an imperfect one. She exits the state if she gets to 10 Cinder Chimes.
Nita also exits the state if she doesn't click at all and the minigame bar reaches the end.
Given that the second punch deals less damage, and the 5th and 6th punches deal much more damage, you want to keep Nita in the state so she can do all 6 punches.

The punches deal 16%, 12.8%, 16%, 16%, 32%, and 68% damage, respectively. These are based on Nita's Max HP, not her ATK.
If a punch isn't perfectly timed in the blue region, then as stated above its damage is halved.

Nita can dodge without exiting the state.

With its first Neuronic, if equipped with a Thermal wewapon (i.e. hopefully always) the last punch will heal Nita for 25% of her Max HP and reduce the cooldown of her ult by 6s.
This allows Nita to fully restore her HP by doing four full combos of her standard skill, which will also reduce the cooldown of her ult as well.
This Neuronic is critical for Pulse's damage rotation to function at all.
Without this Neuronic, using Pulse's ult is basically a death sentence, as it reduces her HP to basically nothing with no way to recover any HP.
Without this Neuronic, Nita will have no way to recover her HP, so she can either use her ult once and just remain at 1% HP for the rest of the fight, or just not use her ult at all.
Given how much damage her ult does, both of these options are terrible for her dps.

An Important Note on Survivability:

Nita's ult removes 99% of her current HP.
Even with extremely high Max HP, this will leave Nita with basically no HP - How much will vary based upon her investment, but generally around 5-700 HP.
Getting too many Cinder Chimes from her Standard Skill causes Nita to lose 10% of her Max HP.

Losing 99% of Pulse' current HP and then taking 10% of Pulse' Max HP as self-damage will kill Nita.
You can do this outside of combat and without any enemies or external damage sources.

Even without damaging herself via her Cinder Chimes, losing 99% of her HP will leave Pulse with basically no HP, meaning she'll probably die very quickly unless she has some of her survivability and healing-focussed investments:

The Neuronic for her ult that gives her a shield after using her ult, allowing Pulse to survive until she can recover her HP
The Neuronic for her Standard Skill that recovers 25% of her Max HP after using the final Smash
Her second Auctus Drive buff, which restores some of her HP after each non-final punch of her Standard Skill

Pulse works better the more of these investments she has, and with none of them Pulse's survivability is so bad that I recommend that you do not play Pulse at all.

Also: Nita's Deiwos effect "Decreases DMG taken by 15%" doesn't affect how much HP she loses from her ult (as she doesn't technically damage herself, she consumes her HP)

Support Skill

Nita blocks attacks for a few seconds, then deals AoE thermal damage in front of her.

Like all main dps operatives, her support skill isn't much good, and you really don't want to use Nita as a support operative.

Weapon

Timeless Rhythm
Her 5* weapon, and her best weapon.
This increases Nita's Max HP.
With Timeless Rhythm, a perfect timing on her standard skill doesn't give her any Cinder Chimes.
It also gives her Skill DMG if above 40,000 Max HP.
Skill hits also cause enemies to take more Skill Dmg, which is a great damage increase.
Scarabaei
The 4* event weapon of Siris - Ksana. Since Nita is an Auctus Drive operative, she doesn't get a 4* specific to her, but Siris' weapon is actually perfect for Nita anyway.
Max HP and Thermal damage, which is good, with more Thermal damage based on Max HP.
It's nowhere near as strong as Timeless Rhythm, but it's easily her next best choice.

Since Nita gets her 5* weapon from her event, there's no reason to ever actually use a 4* weapon, as her 5* is so easy to get.
There are only two shotgun barrel attachments that give Max HP, so if you don't have Maritime Scout for the other [better] one, then Scarabaei is still a useful weapon to get in order to get the attachment that gives more Max HP.

For weapon Parts Nita wants max HP.

Logistics

Squad

Use Sorbus squad - it was designed specifically for her and is her best choice.
It gives Pulse +60% Ultimate and Standard Skill damage.
(It's buffs are timed, but if playing Pulse properly they should be essentially permanent buffs.)

Stats

For stats Nita wants:
10.0% Max HP
+106 Alignment Index
+8.5% Thermal Damage

All of Nita's damage is based on her Max HP, so Max HP and Thermal Damage are the only useful stats for increasing her damage.

Alignment Index gives Nita more healing.
A max-roll of +106 Alignment Index gives Nita +5.3% extra healing, or 15.9% for three.

Since all of Nita's damage comes from skills, and skills can't crit, crit stats are useless to Nita.
Similarly, Nita has no S-Energy or U-Energy problems, so S-Energy and U-Energy regen are useless to her.

Alignment Index

Alignment Index boosts Pulse' healing.
The damage her ult deals is entirely determined by how much HP she has when she uses it.

With its Neuronic, Nita's standard skill restores 25% of her HP on its final hit, meaning that with that Neuronic she can fully recover all of her HP in four standard skill casts.
(or three casts if she has enough Healing Bonus)
Combined with Nita's Auctus Drive, she can also heal from the non-final hits of her standard skill, which allows her to fully heal in two standard skill casts.
Pulse cannot get enough healing and Healing Bonus to fully heal herself in one Standard Skill cast.

With her Neuronics and Auctus Drives, Pulse can fully restore her HP to max in two Standard Skill casts, and she doesn't have the cooldown recovery to be able to ult after every Standard Skill cast.
(and it isn't worth investing into Skill Haste to be able to do so)
Since she'll be at max HP every time she ults, the extra healing from Alignment Index doesn't help her damage at all.

Alignment Index only increases her damage if she wouldn't be at max HP when she ults without the Alignment Index.
This can happen if Pulse is taking a lot of damage, but isn't something you'll encounter often.

Alignment Index is Pulse's second best stat (after Max HP), but Alignment Index doesn't really help her very much at all except in some niche circumstances.

Healing Bonus

Much like Alignment Index, Pulse should be at max HP when she ults after every two Standard Skill casts.
This means that Healing Bonus doesn't normally affect Pulse's damage, although it can potentially buff survivability and damage if Pulse is taking a lot of damage.

As a Special Stat though Healing Bonus competes with Thermal Damage.

Since Thermal Damage buffs all of her damage, Thermal Damage is by-far the better stat offensively.

Pulse doesn't need Healing Bonus, but Thermal Damage is a good damage bonus.
As such, Thermal Damage is Pulse's best Special Stat, although if you don't have much investment into Pulse yet then Healing Bonus can still be a decent cope stat.

Auctus Drive

A1 gives the final hit of her standard skill more damage the fewer Cinder Chimes she has.
If Nita has her 5* weapon, a perfect combo doesn't give her any Cinder Chime, but without her 5* weapon she'll always have at least some Cinder Chimes.
The damage from her standard skill is 0.5x, 0.4x, 0.5x, 0.5x, 1x, with the final hit doing 2.125x.
As such, increasing the damage of the final hit by 50% only increases the total damage of her standard skill by 21.1%
Factoring in the damage from her ult and two standard skill casts (because A2, below) Nita's A1 increases the total damage of her rotation by 16.2%.
Certainly good, but less than the "50%" figure would initially imply.
A2 restores HP whenever Nita punches with her standard skill - 4% for a perfectly timed hit, and 1% otherwise. The sixth/final hit doesn't heal.
Since there are 5 regular punches in her standard skill, with A2 her standard skill will heal for 20% of her HP if perfect, or 5% if you incorrectly time every hit.
This is a really nice survivability bonus for Nita.
A2 allows her to fully restore her HP in two standard skill casts, down from 3 or 4 without it, increasing her damage by a huge amount as she can ult much more often.
A3 reduces the number of Cinder Chimes Nita gets when she fails to perfectly land a punch on her standard skill from 4 to 3.
Obviously this doesn't help you at all if you perfectly time each one, as with her 5* weapon Pulse doesn't get any Cinder Chimes at all on a perfect timing.
Since Nita won't get to the max Cinder Chimes without multiple non-perfect hits, even without A3 you're unlikely to actually fail her standard skill combo.
A3 is thus mostly useless for most players under most circumstances, but it can sometimes help save a bad combo.
A4 gives Nita a 15% Skill dmg boost for 5s after her HP changes.
This means it will proc for both her ult as well as her standard skill (due to A2)
A decent damage bonus, but nothing more.

As an Auctus Drive operative, you'll generally have all of Pulse's Auctus Drives, or none of them.

Good Supports for Nita - Pulse

Nita deals entirely skill damage, so any support that buffs skill damage will be good for her.
Nita also deals Thermal damage, so Thermal-damage buffs are also useful to her.

Unlike most main dps operatives though, all of Nita's damage is entirely based upon her HP instead of her ATK.
This means that buffs to her ATK do not benefit Nita in any way at all.
This makes support operatives who can only buff ATK (e.g. Eatchel - The Cub) potentially completely useless for Nita.

Since Nita can't benefit from most support-based weapons (e.g. Strawberry Shortcake, Lapis Lazuli, or Deep Sea's Call), there's no point in using these weapons to buff Nita.
This means that almost all the 4* operatives are basically incapable of actually buffing Nita, with Chenxing - The Observer being about the only useful one due to her skill damage buffs.

Nita's extremely high self-healing means that healers are not overly useful to her either.

Support operative that work well with Nita - Pulse

Vidya - Celestial Swan (and other resistance shredders)
Celestial Swan and other resistance shredders (Acacia - Kaguya, etc.) that reduce the enemies resistance help enemies take more damage.
If using Celestial Swan, make sure the other support isn't off-element to Pulse.
Siris - Freefin
Nita deals skill damage very rapidly, allowing her to easily gain Siris' Wavehunt, and maintain Freetide quite well, and Siris provides lots of skill damage buffs to Nita.
Siris' +ATK boosts are wasted on Nita though, but she's still a great support for Nita.
Marian - Aquila
Aquila provides very strong generic damage buffs, which makes her an excellent support.
Aquila is off-element to Pulse (Aquila constantly deals Kinetic damage).
Marian - Riptide
Riptide provides some nice skill damage buffs to Nita.
In addition, having Marian swap in to magdump can allow you a little bit of time to reposition without affecting your dps, as Marian's mobility is slightly better than Nita's.
Given how terrible Nita's mobility is, this can be quite useful.
Note that Riptide is off-element to Pulse (Riptide deals Chaos damage)
Mauxir - Shadow Ka
Having a stationary target to use as a punching bag is very useful for Nita, but less so against bosses that are always staionary anyway.
The extra damage Mauxir gives is always nice though.
Chenxing - The Observer
Chenxing's skill damage buffs are nice.
Given that Nita doesn't really like to move much, Chenxings PBAoE nature is often perfectly fine with Pulse.

A lot of the usual cope Supports like Agave and [Redacted] etc. don't work with Pulse as Pulse can't benefit from the ATK buffs that such cope supports typically give.
As such, Pulse doesn't have many cope supports.

Tess - The Magician is wasted on Pulse, as Pulse' ult requires 0 U-Energy, and hence giving Nita more U-Energy doesn't help her dps at all. Tess' damage buffs are still useful, but overall Tess isn't a great support as her damage buffs are weak in comparison to actual skill damage supports like Freefin.

Since Pulse never actually shoots anything, she'll never charge the Zephyr Machine from Enya - Exuvia's support skill, and hence it will never deal damage.
Enya's skill damage buffs are still ok, but overall Exuvia isn't a great support for Pulse.