Wario Land 4 - Catbat (Super Hard mode)

The boss of Sapphire Passage. I freaking HATE this boss. Only in Super Hard mode, though. It's practically impossible to beat him the normal way in 1:05 (the time you need to get the best ending). Therefore, at the end, you need to keep bouncing above him in a similar manner to the final boss in Wario Land 2. This is difficult, though, as he can move unpredictably and cause you to fall off onto the bottom. And if that happens... you're pretty much forced to restart the boss. I had to restart this boss more than any other boss here, so this was frustrating. He's the easiest boss in Normal or Hard mode, though, as you have an extra minute, which is enough to allow you to beat him normally.

As a side note, it's actually possible to attack him without relying on the waves -- this saves a TON of time if done correctly. When he unleashes a wave, he dips down, which is low enough for you to attack him. This is even harder to do than bouncing on him repeatedly, though, and I have only been able to do it a few times from sheer luck. So I didn't bother doing this tactic here.