Warhammer 40,000: Darktide

Instead of a grenade like the other classes, the Psyker has a skull icon for their ability where they focus energy on a target and call down a lightning bolt that will strike the target's head and kill them instantly for smaller targets. Press down on the D-Pad to switch this mode, you'll have both hands out with no weapons and button prompts on the screen reminding you how to use the ability.

Pox Hounds are big, red dog looking monsters, you'll know they're near because you'll hear them barking, or the squad members will comment on them approaching.

Now, don't misunderstand, you're not required to get perfect timing and kill the target with your Brain Burst while it's still in the air, I targeted by one of these dogs, started charging the ability, dodged its pounce attack, and the lightning strike hit after it had already landed behind me.

The game seems to give you some extra time, just make sure you target the dog and start charging the ability before it starts the pounce since it takes several seconds to fully charge.

pouncing Pox Hound are the Dogs which are howling. As stated, you have to use the psykenetic and use his Attack on "G".
The key seems so be, that the hound is charging at YOU. When he is charging at someone else, it won't pop the Achievement.

thanks for the added Tips in the comments. My Solution was written asfter first day of PC release.