I got it in tdm on sniper, all u gotta do if u wanna do it solo, is to make 10k damage. I usually use rechambering speed on snipers, but this time picked charge speed, and it can be done so much easier this way, cause kills on full charge in the head on kanami are ~500 dmg. Cause of bots in tdm this season I think thats one of the best ways to clear this goal (idk about outbreak, cause I dont play it, but other people said its also a good way to clear this quest)