Hardest boss of FF IV?

What do you think, who was the hardest boss?

For me, I think Odin was the hardest as well the coolest. I found the fight very cool and the fact I had like 30 secs to beat him awesome and original. It also made it very challenging and beating him before level 45 Rydia was very hard. I did manage to do it, but barely.

Also, many tell that Evil Wall is one of the most challenging bosses ever but I found him easier than Odin. Of course, I had some troubles with him but I never died when I was facing him.

After playing the DS version, I got to change my opinion.

In the ds version, Odin isn't as hard as in the psx one.
Anyway, the hardest boss. Proto-Babil. With a full 99 party with the best gear in the game ( Although I am missing a few onion items to have a full set) I still haven't managed to beat him. That should show how bloody hard he his.