PlayStation Move Heroes

You might get these trophies during your first playthrough. If not, you can start any challenge with many enemies, like Pinbot Apocalypse in Canals, Paris and use the ultimate ability on Pinbots there for fast progress.

Another good challenge to farm kills is Serious Smackdown Diamond Challenge in Metropolis. There are tons of enemies in this level within a very short period of time. There are plenty of crystals to power up your special attacks quickly, and the enemies tend to storm you in groups so you can get a lot of kills quickly.