This trophy is most easily acquired with any of the characters that have a melee type level 1, like Raiden.
Easiest level by far is the Burning Cargo Plane. You start out in a space barely big enough to move, and you can almost hit everyone with little to no setup. I got this with Big Daddy on my first try, so you should be able to do it with relative ease with most of the melee Level 1 characters.