Psykitty - Psychic Vampire - CG
 Psyker Build - Warhammer 40k: Darktide 

Powerful yet versatile build. Use VoidBlast to build heat. Malefic Momentum + Empowered Assail = melee beast + toughness recovery.

Horde:
Hit the first wave with back-to-back VoidBlast (VB) uncharged secondary attacks to spread SoulBlaze (SB) until you start to overheat. Hit your ability and mix alternating between VB and Assail until you start getting up to medium heat and to build Malefic Momentum (MM) stacks, then switch to your GreatSword (GS) and start cutting the hoard down, mixing in assail for free toughness regen via Empowered Assail (and for MM stacks).  Usually at this point you can work in a (90+% heat) Warpshock to finish the hoard off.  When the heat starts dropping use VB to bring it back up.  The GS only shines at high heat.

VB secondaries can be charged longer to knock Ogryns down at your feet and then decapitate them with the, great for Bulwarks.  The melee really shines in boss and monstrosity fights, but try to keep SoulBlaze on them as well, it might not seem like much but it adds up.

Some notes about the Mk VI GreatSword, it has a complex pattern with undocumented attacks hidden within:  3x lights, then a heavy will result in a heavy hitting high cleave L-to-R attack, more than 2x the damage of the light attacks, this is how you clear hoards so quickly without even using Warpshockwave.  When you switch weapons to your sword, it will be "unsheathed" from the left before being lift up on your right shoulder, if you attack quickly enough, light or charged, it will start with a faster L-to-R attack, quick-draw Iaijutsu-like.

This build does it all, except overwatch but it can shoot down a sniper if it really needs to with either aimed Assails or VoidBlast rapid fire primary.  You feel invincible until you're not.