Oh hot damn O2. I still posit that out of the Kirby main villains, he's easily the most intimidating. I appreciate how you got that sketched feel that defines Kirby 64's look. The light source was well placed and I like how his shadows are strongest at his back. O2 is an abomination at its finest in a game played by young'uns.
Usually, yeah. I mean, they're not outrageously gory or what have you, but they stand out as the exact opposite of the bright and colorful world you've traversed through. Essentially, Dark Matter, Zero, Nightmare, Dark Nebula... whoever was the final boss in the mirror game and the Wii game... they're all antitheses to the world.