My favorite was either Airbuster or the very last boss fight in terms of gameplay. Really fun, hype fights. A lot of the boss fights in this were great though and a really fun time. The only times they weren't were the marathon before the end, and that may have just been me not understanding them.
I could not figure out for the life of me the gimmick behind Jenova's last phase since I kept killing the tentacles, she would become vulnerable, then I would stagger her and she would become what seemed invincible since she would push back everyone who got close and become immune to magic. Maybe if I had Breach on me I would have been able to dispel it and hurt her, but without it, I really had no idea what to do since any physical attacks that made it through also triggered a huge counter.
I also didn't understand Arsenal's first phase, since the probes protecting it said they were resistant to long-range and magic damage, but... your party is Barret and Aerith, so those are literally your only options. That combined with how much health Arsenal had just drug out the fight a lot.
For Rufus, it also became boring during the later phase because he would counter everything and I could never quite hit the opening to attack him and gain ATB for Braver, so I just ended up guarding forever until ATB built up enough to try and land a Braver on him. It felt like a trick fight at that point where you kinda had to wait for the ability to use the one right move and couldn't do anything else. The rest of the fight was great though!
