The Last Guardian – Losing Their Minds Trophy Guide – Defeat 10 or more suits of armour by removing their heads. [Gold]
Sometimes in combat Trico will knock down the suit of armor enemies and they don’t die instantly. When this happens they usually stay on the floor for a few seconds before getting back up. While they are on the floor you must walk up the them, hold the Circle-Button and push the left controller stick near their head. This will let you tear off their heads. Repeat this a total of 10 times.
A great farming spot for this is at the end of the game on your way up the last tower. Here you will have the two largest enemy encounters in the game. There are some stronger suits of armor (white armor) that can take up to 3 hits from Trico. Wait for one of them to get knocked on the ground and tear off the head quickly. Restart checkpoint before the battle ends! The game creates an automatic checkpoint after the fight.
You can farm this via checkpoint restart! It can be done over multiple playthroughs. Your progress carries over into New Game+.