That horseback boss fight in TP. Oh my god, I almost quit playing the game because of him.
The first time I faced him, I had to do it probably 20 times. I simply couldn't figure it out and was getting really, really, frustrated with it. Finally, I somehow beat him... but only to find that he comes back later in the game - stronger, too. I was so mad. I can't even remember how long I was stuck on that but it was pissing me off. I resorted to having to read many different walkthroughs, which didn't help at all. Somehow, I beat him though.