Loonyland/YMMV

Ensemble Darkhorse: The Bodhzas and Gorkas.
That One Boss: Gourdzilla, since it has a massive legion of Yellow Roses that frequently get in your way while trying to reach it, even when you're in range to attack it.
- Killbor, despite not having any special abilities, can hurt you for a lot of damage. In addition, he has a lot of health and can frequently spawn Nuclear Bokboks that explode on impact.
- And don't forget the final showdown against the Happy Stick Bird. Not only does it frequently switch between the elemental affinities of fire, ice, and earth, but the attacks from each individual element cover a huge chunk of the battlefield and dish out some serious pain.