This trophy is a bit glitched. If it doesn't pop for you, go find one of the large gates. Grab and hold an enemy in your jaw and then tail-whip it at the gate switch. The easiest gate to get to is in Caviar Key. Fast travel to the grotto and head left towards Fawtick Bayou. Once the gate opens, the trophy should pop. This glitch seems to happen if you 100% all regions before the final boss. I hope this helps!