Double Attack

Kill 25 heavy enemies using the Time Rewind double attack.
The time rewind double attack can only be done against certain enemies: Brutal Mauls, Brutal Zombie Heavies, and Skyguard Heavy Infantry (the giant guys with the backpack that regenerates their health; and it's questionable that they actually count, seeing as how you only use your Time Rewind to disable their backpacks, not to actually kill them).

This is how the time rewind double attack works: do enough damage to the enemy and you'll get an R1 Button prompt above that enemy; hitting R1 Button makes you jump on the enemy and you'll then get a Square Button prompt - tap Square Button and Ayumi will start to pound on the enemy until he shakes her off; once Ayumi has been shaken off, hold down L1 Button to rewind time until you see Ayumi's "clone" jump onto the enemy and start doing that pound move, let go of L1 Button, and if you're close enough to the enemy you'll get another R1 Button prompt - your "clone" will jump off the enemy as you jump onto him, and this will result in the finishing move that is required for this trophy.

Even with frequent deaths you will probably not get this by the end of the game; statistics do carry over via chapter select, and you will probably get this during your second playthrough, but there is a place where you can easily farm these kills if you want to, and that place is the final room of the ninth chapter, Brutal Town: it's a large room inside the castle, and when you enter it the first time there will be several Chaos Observers you'll have to deal with; killing all of them triggers a new wave that includes a couple of Brutal Zombie Heavies and several Brutal Zombie Fighters - this move can only be done against the Brutal Zombie Heavies, of which there will be two; once you've killed both of them, let yourself die and the checkpoint will restart.