I found the fastest way to boost this is with 4 players/ accounts, 2 idling and 2 going for kills. (thanks to boosting partner Healtti
for discovering this way with me).
Start up a Ranked deathmatch on Labbrats, time limit 30 mins (or shorter if you don't want to do half an hour), kill limit to 0.
Have the 2 idling players/dummies standing on the 2 spawns downstairs, the 2 active players who go for the kills will go upstairs. There are 2 spawns pretty close to one another up here. The idea is to keep throwing grenades at each other. We would BOTH get about 210-230 kills every match, depending on how quick we got the dummies, set up, how quickly we kept respawning and throwing nades and on how often grenades would not kill us.
-You can throw grenades via the wall, to save some time every time.
- There is a respawn glitch which lets you skip some of the 5 second countdown. Upon dieing, press
to swap character, then change character with
, then spam
. If you can't pull this off, it will often only work after 2 seconds (so respawning in 3 seconds...).
-Try to avoid throwing the grenades near the pillars and the staircase. There are some invisible walls around the pillars. Besides, if the grenade is on a different altitude than you are (at the staircase), you might not die.
With this method, you should be able to get the kill related achievements done for 2 players in about 12 30 minutes sessions, thus about 6 hours.
This one should also pop: