But hmm, dark. Trying to think of what I considered dark when I first saw it, in which case that award definitely goes to Piccolo Daimao. Goku has his first dose of bloodlust, which the plot has no time for as he gets hammered by Piccolo after a couple good shots, and three heroes and the freaking dragon (That really got me) die. Which makes Goku's refusing to stay down in the rematch that much more epic.
In Z, I've got to agree with Cipher in that I like the tone shift in the Sayain fight. It endlessly hypes the Sayains and never quite lets you feel certain that the heroes are prepared, then pumps you up when the gang comes together and you feel like nothing can stop them, then Yamcha ties and it all goes down the toilet. Notice in the anime where the fight starts in the afternoon, but when Goku and Vegeta fly off the sun's setting over the original battlefield? Classic.
Seems Falcouner productions were the only ones that realized that Garlic Jr. is a freaking demon. There really are some Halloween vibes there.