Lot's of incorrect information online about this one. What you need to do is choose Angelia versus anyone else in a Versus match (doing this legitimate is almost impossible). Make sure the timer is set to infinite to ensure you have enough time. With Angelia, hold on to weak attack (Square by default) for 75 seconds and then let the charged hit attack your opponent. You should see no visual cue of an attack being charged but after the 75 seconds is up and you let go there should be an animation of a jumping kick with a lighting flash - and your trophy.
For some reason, many people have said that you are supposed to do 60 seconds which baffles me. The trophy clearly says 75 seconds for a reason.