My top 5 hardest bosses in Kingdom Hearts

These are the bosses in the Kingdom Hearts series. And these are also the ones that I found really hard to beat and some I did eventually beat and some that I'm still struggling at.
5. Vanitas's Lingering Will (Birth by Sleep): Not only is this boss hard but he can kill you with just one move. I eventually beat him when I found out he can be beaten easily by using Tornado as Ven. But if don't have that, you're in for a really hard boss.
4. Sephiroth (Kingdom Hearts, Kingdom Hearts 2): Oh, yeah. This guy has so much power and strength that he can kill you in under 2 seconds in a fight. The hardest was probably in Kingdom Hearts 1 because his moves are so unpredictable. However it is more satisfying to beat him in Kingdom Hearts 2 because there's a really cool cutscene after it. Watch.

And after that you get the Fenrir keyblade which is one of my favourites.
3. Data Xaldin (Kingdom Hearts 2.5): Good grief. I can not count how many time I had to redo this fight over and over. Not only was he really hard but on top of that, every time I got close to beating him and died, I screamed with fury because I was really annoyed. And when I did finally beat him I said "phew" so hard.
2. Marluxia (Kingdom Hearts: Chain of Memories): Oh, my god. I struggled on this boss for years. I mean literally years. For a while I didn't play this game on the GameBoy for years until Halloween last year when I finally beat him and I've never felt more satisfied to beat a boss in my life. But it's still not as hard as number 1.
And the number 1 hardest boss in Kingdom Hearts is...Mysterious Figure (Birth by Sleep): Good God. I don't think anyone's ever beaten this boss. I bet a lot of you were expecting the Lingering Will from Kingdom Hearts 2.5 to be here but I've been able to beat him 2 times already. But this boss was no mess around. I've never beaten this fight ever. His attacks are so deadly he can kill you within in an instant. It's actually just young Xeanort and it so weird that a really easy boss in Kingdom Hearts Dream Drop Distance was a madhouse of power here. He always does thing to your attacks to either stop you from using them on him and good grief, has move when he scatters your moves all around the place and you can collect them but you need to be really fast to do it. And he barely lets you heal. And that's why the Mysterious Figure, A.K.A young Xeanort is my choice for the hardest boss in the Kingdom Hearts series.