The bosses of JJ2 seemed a little too easy, but compared to the scripted bosses (Move to point A, attack no.1, wait, Move to Point B, attack no.2...) found in JJ1 and most other platformers, they are a little toughter.

Userlevels in JJ2 attempt to add more difficutly / increase battle time by using multiple bosses. I feel this works okay, but It should be best used on the "Insane difficulty".

Depending on who made the level, the toughest (to hit) would be the rocket turtle.