GigaBash

Can be completed offline in couch play with 2 controllers or with just 2 cpu players aside from yourself.

Select 4 player battle, make sure there is at least 3 players, you, 2nd controller, and cpu. Die off in the lava so that you come back with Post-Death, injure the cpu until they have 1 life left, and use the post death to deliver the killing blow on the cpu player.

Select Online, Public, and Free-For-All.

When you are defeated you have the ability to use a targeting system by pressing X. It has a slight recharge delay. When the battle has two remaining Kaiju, aim at the one with the lower health and press X. If you successfully get a hit on them that knocks them out of the match, the achievement will unlock.