Unreal Tournament III

This would be the hardest trophy in the game, if it weren't possible to heavily manipulate the game settings in your favor.

Required Setup
Gametype: Deathmatch
Map: Heat Ray
Mutators: Weapon Replacement (All to Impact Hammer)

Heat Ray is the map mentioned before that has the Dark Walker spawn on it, which makes it very easy to kill the bot once it spawns, because the bot doesn’t know how to deal well with the Dark Walker. Once the match starts you basically have to hide and run away from the bot until the Dark Walker spawns, then get in the Dark Walker and get 20 kills against the bot using it. You will have to watch out for the bot when it picks up the Bio Rifle that spawns on the map (which you can’t remove with weapon replace) as it is very good at lobbing shots and hitting you from far away. I found that the bot would seem to alternate spawning on sides of the map, so you can easily hang out near the Dark Walker spawn and take it out as soon as it comes into view. As long as you the Dark Walker isn’t destroyed before you get to 20 kills this trophy should be relatively easy.