I never thought about this until I went into an Interchange run yesterday with an Ash-12 i built for a total of 120/130k. Long story short I spotted Killa running at me from the German phone store (the one opposite to Mantis) with his head sticking out from behind one of those concrete things next to the escalators. Domed him before he could get out of cover and destroy me. Thought I was dead because of the 46 pen. Didn't die, Killa succumbed to that godly 102 damage. Looted him and got tf out of here before the usual chad running m61s could kill me and made a cool million selling all his stuff.
So, TL;DR: Ash-12 with PS12B (600 roubles) kills Killa in one shot to the head, the whole build costs around 120k, do what you please with this information.
Edit: I once did this by spamming his head with ps ammo using an SKS, but got killed by some PMC before I could loot him.