I'm in the top 10 mood, so here we are with another top
No comic relief and redeemed villains
10) Fawful: some of you may be surprised to see him so low, so let me explain: while he commits a lot of crimes, his most evil crimes are ordered by Cackletta. In BIS while he shows to be smart and prepares such an evil plan, he still doesn't cause much trouble: the virus he spread isn't deadly, he didn't kill anyone and we don't know if he knew about the Dark Star's behaviour. Bowser and a lot other villains commited worse crimes.
9) Bowser: the big bad of the series deserves a spot here, not only because of the fact that even after 30 years he's still here causing troubles, but akso because of his crimes: he constantly kidnaps Peach, he turned milions of Toads in bricks and goombas, he took over the Universe twice stealing all the super stars, he caused troubles aroun the world by stealing important treasures and terrorizing people with giant mecha wigglers. While he's got a good side, he still deserves to be here.
8) Dark Star/Dark Bowser: He's so low in the list because we only see him for likely less than 30 minutes of gaming. Sure he caused troubles and attempted to destroy the Mushroom Kingdom, but still there are other villains who caused more trouble.
7) Antasma: He's the responsable for the fall of Pi'illo island. When he came back he attempted to rule the world alongside with Bowser (while they were both using each other, the Koopa King played his cards better). When Bowser betrayed him he planned to brutally kill him but he was defeated by Mario an Luigi.
6) King Boo: He attempted to trap Mario and Luigi inside paints to get rid of them and rule the world. What makes him particularly more heinous than other leaders is the fact that he doesn'care about his minions, nor he never shows gratitude to Hallen Gravely who freed him.
5) Cackletta: She is pretty sadistic and vile: she attempted to steal Peach's voice to use the Beanstar. Also she brainwashed a lot of people, such as Queen Bean. She also manipulated the Bros. and Bowser's minions as Bowletta.
4) Shadow Queen: She tried to destroy the world twice, she possessed Peach and she killed Gordus. Also she murdered the whole audience when she got angry during the final battle. Pretty high heinous standard.
3) Princess Shroob Sisters: They were the leaders of the Shroob army and well... they literally attempted a genocide. They drained life out of toads, leaving them to an horrible fate, destroyed towns and attempted to take over even the Future Mushroom kingdom.
2) Dimentio: This guy is insane: he tried to take over the Universe by destroying it and recreating another one, he also manipulated everyone in the game, including his own boss, only to show up at the end, betray Bleck and take Luigi and the Chaos Heart for himself. After his defeat he tried to leave a fragment of his power in order to still destroy everything... just wow.
1) Bowser (movie): What happens if we take away every good quality from Bowser and turn his love for Peach into obsession? Here's the result. He lost even his respect for his minions. He even attempted to kill Peach after he was rejected, but the worst part is the fact that he wanted to sacrifice people for no reason, just to make more "spectacular" his wedding, showing that he has no respect for people's life. He's the only one in the Mario-versr who killed because of stupid reasons... give him enough resources and here's a Frieza in Mario-verse.