*Possible Minor Spoilers*
This trophy is for killing both of the panthers during Chapter 14 (Or Final Chapter), whilst wearing the "Brandon" Panther mask. However, the Brandon mask can only be obtained by beating the high score in Chapter 17 - Fun & Games, so you will have to go back with chapter select after finishing the game. Simply load up chapter 14 again, select the brandon mask and fight through to the panther part of the boss fight. As soon as you have killed both panthers, the trophy will pop.