I know that this is technically the wrong thread, since this is on my PS2 copy, but...
Back in the day, when I played KHIIFM every single day, I decided to try out a Critical mode lvl 1 run. I remeber struggling for an entire day, with, first, the Dancer Nobodies and then Demyx in Hollow Bastion. And after finally defeating Demyx, I was not going to risk dying and having to fight him again, so I let the FF characters do most of the work in the following segment, until I hit a safe spot.
That was my prime in KH.
However, I then encountered Jafar, and the Experiment. I simply could not defeat those two bosses at lvl. 1, and after a few days of agonizing deaths, I gave up, made a back-up safe file, in case I ever felt like trying again, and continued my playthrough as a low level playthrough. That was the Summer of 2008.
A few weeks ago, I had finally mustered the strength to pick the playthrough up, and just play around a bit. Just for funsies I tried the Jafar battle, and I had reasonable amounts of fun, so I tried again, and I tried again, and again, and then I had defeated him. "Holy Shmokes!??!? I actually beat Jafar? Savesavesavesavesavesavesavesavesave!"
Then a few days later, I beat The Experiment. I was, and still am, overjoyed that I have overcome the obstacles that hindered my playthrough those 7 years ago, and now only two storyline bosses, whom I had trouble with on my low lvl playthrough, stand in my way for a completed game on lvl. 1.
Those two are:
Xemnas' Dragon: It was only a challenge on low lvl because you cannot heal the entire fight.
Roxas: He is simply a beast, but I did spent my entire Friday morning, just fighting him for fun, to get somewhat accustomed to his moves. Yes I have been playing the game since 2007, but on my regular lvl. 99 save file, I have never noticed his moves in the Data battle, and just gone Auto-Drive -> Limit Form whenever I get in Critical condition, and then I spam him with OP combo finishers. So I have never really learned how to deal with his moveset, so that is now my next step.
I have have very much enjoyed playing KHIIFM again recently, and the progress in lvl. 1 just makes me so much happier! \o/