Err... those are actual bosses, not mini-bosses. The mini-bosses of Kirby would be like the larger versions of regular enemies, like those bomber guys, or the ice walrus dudes, or whoever.
Also, this thread needs moar pics.
My vote is for Dyna Blade. Its just a badass name.
I decided to post pictures of some of the bosses.
Marx - The final Boss in Kirby Super Star. He was friends kirby in Milky Way Galaxy, then waited until he gathered all stars, and betrayed him.
Twin Woods - Boss in Milky Way Galaxy. They fused this time.
Invisble Charmellon - Boss in Cave of Great offensive. He eats you, then spits you out and can turn invisible.
Dyna Blade - Bird who roamed the skys in rage. Kirby defeated him and help her/his babies.
Whispy Woods - The all around basic kirby boss.
Heavy Lobster - Boss in Halberd. He first chases you down the level, then you must fight him at the end. He has a flame thrower, mini-projectiles, and can jump very high.
RPG Boss - You have to fight 3 of them in RPG style. They appeared throughout the game in Great Cave of Offensive.