Could be A pretty fun character too play 😄

This honestly sounds like an amazing quest giver.

Evil Quest Giver: Yes, go and fight the dragon in this remote mountain and get treasure! I hope you survive, hehehe...
Party: (One week later) Wow, that dragon was kidnapping the locals and planning a conquest of the valley! Good thing we put a stop to that, huh?
EQG: Uh... Holy heck... W- Well, you're just the people to deliver this letter to this outpost in the middle of nowhere! Go now, take your time with the trip!
Party: (One week later) Turns out the guy you sent that letter to was researching occult rituals and accidentally unearthed a swarm of demons. We saved him and found this sword of sacred might.
EQG: Okay, plan C. Join me, and we shall overthrow the crown!
Party: The one terrorising the common folk? We were hoping there was a resistance group we could join!

So basically Despicable Me? Maybe with a hint of Megamind?

Their enemy is the Monkey's Paw Paladin.

They are constantly having to come up with terribly evil things to inflict upon the world in order to make the efforts of the wannabe evil enemy work out well for everyone.

A thankless task, really, but what else can you expect when you serve the Monkey's Paw?
- Monkey's Pawladin?
- Titan/Tighten, and Metroman.... Yeah that matches up quite well....

Of course, once the all powerful ruler, they now have access to villainous schemes only dreamed of!

Which all spectacularly backfire and bring the world together in prosperity and understanding.

What’s the opposite of “task failed successfully”?

Task succeeded horrendously

reminds me of the episode of adventure time, when marceline (the vampire queen) is first introduced.

it reminded me particularly not of the first introduction but the one that finn and her become buddies
- ah, right.
  
  Yes, I mean the ep where they became buddies. I forgot about the first one with the house.

So if he tries to do good, does that also backfire, or does everything become a good deed regardless?

The prompt only says the villianous plans backfire
- Ah, true. So trying to do good won't help him do evil, either. What if he tries to do something morally ambiguous, like stealing bread to feed a starving family?

Literally this video: https://youtu.be/GPUgjy-Pn-4

You'd escalate. Right? You'd have to see how far the universe will bend to make the ends justify your means.

"Lord Despoiler, why are you planting a nuclear bomb under that handicapped puppy orphanage?"

"Because I've lost control of my life."

Veigar from LoL