Here the same tactic as in the
But for this trophy, you need to do this with all six characters one time each.
The trophy will pop when the levels boss is beaten. However it is noteable that you don't need to play an entire level. For example, if you start at the "Main Stage" checkpoint of Level 3, all you need to do is to defeat the boss Todd and the trophy will be unlocked.
As a sidenote: Even if I already have won the "Wallace the novice" trophy, I still had to play a second time with Wallace before the trophy unlocked. It is important to watch out for the piggybank save symbol at the end to ensure your progress is saved.
If the trophy wont pop right away after you have finished with all 6 characters, try to replay with various characters. At some point the trophy will pop. No glitches known at my end.