Item description:

Go forward down and you'll see the boss area with the ape. Defeat him and after dealing the final blow press R1 one more time to cut the worm thing off. Be aware the prompt can be hard to see because of the message you'll get about beating the boss. Just keep presing R1 and you'll get both trophies.

Save file is modded with max health and attack, so it should be easier. Be careful though, the ape screams sometimes increasing your fear status. Back away a little bit when this happens, so you won't die of fear, since my character doesn't have Pacyfing elixir in his possession.