Jihadist Jinx
 Psyker Build - Warhammer 40k: Darktide 

Main idea for this build is maximizing the offensive potential of Crystalline Will, since it's been updated to not corrupt one of your wounds if it kills an elite enemy.

*Requires an Illisi Mk V Blaze Force Sword with terrible Warp Resistance. I got lucky and was able to get one with 0%, allowing me to get to max peril in 3 special attacks (Each one adding 45% peril, so you'll want to get one that generates at least 34% peril to reach 100% in 3 attacks).
 

How to Explode?

Build Up
Spam special light attacks until you reach max peril. At max peril, use the combo (Heavy -> Light, x2) to do damage until your peril passively decreases. Once you're below 100% peril it's safe to do another special light attack, so you can repeat the combo forever. Repeating this combo at all times allows us to always be at high peril, ready to explode when a wave of elites appears out of nowhere.
 

Light Special -> (Heavy -> Light) -> (Heavy -> Light)
 

Release

When you're ready to explode, make sure you're at 100% peril and do a force push to trigger it (Hold block and the attack button) while also dodge sliding away from your targets. The dodge slide will add some room between you and all enemies, the push will get nearby chaff off of you, and the force push can knock down one dangerous enemy before the explosion sequence commences. I like to use the force push on the elite I specifically weakened to make the blast free, since throwing them on the ground lowers the chance a teammate will focus and kill them before the explosion. Also keep in mind that the force push only generates peril if it connects to an enemy, so if the enemy you're targeting dies before it connects you'll avoid unnecessarily corrupting a wound.

Dodge Away From Enemies + Slide + Force Push 
 

Positioning

If there are a large group of elites, use your ranged weapon to safely approach and then let yourself explode! I chose the Sustained Fire blessing, since it incentivizes you to mix in slides between shots to stay on the offensive. See my previous build on how that works in detail (https://darktide.gameslantern.com/builds/9f7abc29-2197-415a-bb77-1e84d6d66f77/quad-burst-sentry). Long story short, constantly sprinkling enemies with a high crit ranged weapon ensures Empathic Evasion is active constantly to keep us safe from gunfire.

When to Explode?

Keep in mind your teammates might kill the enemy before you explode, so I tend to only blow up if I feel I can't take out the enemies fast enough with the sword alone. You'll want to keep an eye out for hordes of 4+ elites, since that's where it starts being worth the risk of blowing up. Exploding takes a few seconds and in that time you are vulnerable to both melee and ranged attacks. Make sure gunners have been melee aggro'd onto you and that you dodge slide away from any woodby melee attacks before letting it rip.

Also if your team is getting swarmed on all sides, it might be worth it to explode, even if no weakened elites are in sight since the alternative is just dying lol. I also noticed the knock back from the explosions can come in clutch for quickly reviving a teammate covered in enemies, so I chose increased revive speed to play into that strength.

What to Explode?

Here's a list elites that can be killed with just a light special attack to head + explosion (No Uncanny Strike stacks) allowing you to explode without consequence more consistently. Keep in mind with buffs active some elites (especially dreg shotgunners / gunners) can be killed with only the explosion.

(Scab = Armored Soldier Variant, Dreg = Unarmored Cultist Variant)

- Scab/Dreg Heavy Gunners

- Scab/Dreg Shotgunner (Dreg version will likely get one shot in practice, since he barely survives an unbuffed attack to the head)
 

- Dreg Rager (Scab version barely survives without buffs)
 

- Scab Plasma Gunner (Wasn't able to test this in the Psykarium, but in practice treat them like Heavy Gunners) 

The remaining elites will require a bit more effort to kill.

- Scab Maulers can be combo'd with 3 head light special attacks and an explosion, but you'll need to be below 10% peril to pull it off. 
 

- Bulwarks can be made vulnerable with a force push for a short window of time, so the combo changes to charge force sword + force push + 2 heavy attacks + explosion. Keep in mind only the heavy attacks will be able to connect before the Bulwarks shield gets in the way, but luckily for us the explosion goes through it.
(Special Button -> Hold Block Push -> Heavy Attack -> Heavy Attack -> Explosion) 

- Reapers are vulnerable to 2 head light special attacks and an explosion but since they're such big targets teammates will often kill them before you.

- Crushers are too tanky to kill with simple combos, so chip damage and teammates are your best bet. 
 

Alternative

Seeing as this build works best when you are launching yourself into groups of enemies, an alternative set up for this build is using Catachan Mk VII "Devil's Claw" Sword and Accatran MG Mk II Heavy Laspistol. You'd have to swap True Aim for Kinetic Deflection so blocking / parry enemies with the Devil Claw would increase peril and once you reach max peril you could use the Heavy Laspistol's special attack (force push) to trigger the explosion. I'd also recommend swapping out Immaterial Focus for Lightning Speed since the Devils Claws attacks are noticeably slower than the Illisi. I also decided to swap out Precognition for Warp Ghost since we can't create peril as quickly, so what little we do make from the force push should be retained as much as possible. Most importantly swap out One with the Warp for Just a Dream. The parrying playstyle puts you at higher risk of chip damage, so this talent is the best way to minimize any mishaps. Definitely more difficult to explode on a dime compared to the main build, since you can only generate peril with blocking / smiting / force pushing, but if you're a parry enthusiast then I highly recommend you give it a shot. 

Small Horde Combo: Heavy -> Light

Dense Horde Combo: Heavy -> Block (Listen for incoming melee attack) -> Parry -> Dodge
Defensive Combo: Block -> Push Attack -> Light 
Offensive Combo: Light -> Heavy -> Light -> Light

This video from Mr. Unc inspired the concept for this alt: 
https://youtu.be/N7TUYA-gg0Q?si=NBA69qYaPvLXTmKh