Encounter: The Duel (Chapter 22)
For this trophy you must beat the endboss without getting hit. You can do this via encounter select on explorer difficulty. If you do get hit you can restart the checkpoint and still get the trophy in the end.
Your opponent's attacks are very slow on the easiest difficulty (explorer). If you try it on a higher difficulty it will be very hard to do.
After beating the game you also unlock the Slow Motion cheat. The cheat does not disable the trophy. So if you have any trouble, enable the cheat and all attacks will be in slow motion, giving you enough time to react.
You must evade his attacks by pressing Triangle/Circle. When he strikes from the left you must press Triangle, when he attacks from the right you press Circle.
My strategy was to quickly press circle at all times. So if he attacked from the right I would automatically block it each time. I only needed to watch out for attacks from the left. When he attacked from the left I pressed Triangle real quick.
For some of his attacks it's hard to see from what side he's gonna attack (e.g. spin attack). It will take some practice to get to know all his moves. After a while you'll get the hang of it. Some of his attack combos are always the same at certain points of the fight. Most of the advanced attacks (like the sword spin) hit from the right side.
Because you're allowed to restart checkpoints it's not so bad. There are several checkpoints throughout the fight.