The Sharpest Wrench achievement in Last Stand annoyed the hell out of me. 350 kills in single match with Mekboy, and I don't have the DLC weapons which would allow me to do a really lethal explosive teleporter build, and the map with far more units, Anvil of Khorne is bugged and will not record results for me. By wave 16, our team will have killed roughly 700 enemies in any case, 350 being half of that meant that I really had to outperform rest of my team
So basically I had to cross my fingers with a trash-killing build that my teammates were either too tanky, or plain too crap to kill many people, assuming we died in Wave 16 of Bloody Colosseum to the doppelgangers. I hate achievements where you have to play excellently while your friends are just crappy enough that they stay out of your way but also do not lose, it's maddening. Especially when there's a bit of gear tied to it.
Thankfully this just happened. My teammate Lord General was admittedly bad at the game, or with the character, and the Space Marine Captain went all in on support and tankiness. Our doppelgangers were impossible to beat as a result, but at least I got 413 kills from it. Lord general was too busy dying and Captain was too busy ressing and tanking/kiting big melee units to kill many enemies