TROPHY NAME -------------------- Hammer of Destruction
TROPHY DESCRIPTION ----- Caused 500 or more damage with 1 attack.
Pretty self-explanatory trophy. You'll get this easily by the end of the game, as the further you progress, the more devastating skills and attacks you'll posess, and you'll also need to backtrack to older areas with weaker enemies.
I got this by grabbing some memories from weaker enemies in the Los Labyrinth, using a thunder-based weapon that the mechs are weak to, combined with the cyclone skill. Did a big 800 damage to all the enemies in the range of it.