PlayStation Move Heroes

This trophy is actually much easier than it sounds, since the 2nd Player actually has the option to use the crystals they collect as health power-ups instead of ammo (on non-timed challenges). I recommend going for this on the Metropolis Diamond Challenge, Serious Smackage. Collect several crystals with Player 2, then switch to the Health Up option by pressing and spam them at Player 1 with the button 20 times during the challenge.