The Plan: 500 years before modern times, protagonist Bryce Boltzmann was forced to witness the demon king Astaroth murder his wife. To cause as much pain as possible, Astaroth then gouged out one of Bryce's eyes, and cursed him with immortality. This way, the couple will never be reunited in the afterlife. As far as cruelty goes, this is an ingenious move.
The Dumbness: Was it really worth it, though? We're talking about a man who has been wronged, and would do anything to get revenge. Also, he is immortal now. As in, he will never, ever be dead. NeverDead, if you will. During those 500 years, Bryce became a bitter alcoholic with plenty of issues, but he also killed thousands upon thousands of demons, so how is that a victory for Astaroth? His sadistic little curse has had been biting him in the ass for half a millennia by the time the game starts.
"Better quit while I'm still A HEAD, Astaroth. Eh? Get it?"
The Outcome: At the end, Astaroth finally realized that giving your enemy immortality is a bad move and actually took it back, only to learn that Bryce managed to absorb a somewhat lesser invulnerability after his battle with the previous boss, Alex. Bryce defeated Astaroth, who was determined to take Bryce with him to hell. Later, Bryce made a phone call to his partner, Arcadia. Either hell has awesome reception or Boltzmann made it out alive, possibly as mortal. This sadistic joke failed to deliver after 500 years of buildup.
The Plan: Archie and Maxie were rival leaders of rival teams with very opposing goals. Archie, Leader of Team Aqua, attempted to wake up Kyogre and use it to expand the ocean to cover the entire planet, because apparently he is the biggest fan of 'Waterworld' ever. Maxie, Leader of Team Magma, attempted to wake up Groudon and use it to dry up the ocean and make more dry land (and, consequently, less drinking water globally), because he is more of a 'The Postman' guy himself (things were pretty dry in that movie, right?). Both were charismatic enough to gather a bunch of loyal underlings to fight for their cause. That is somewhat surprising considering the fact that...
The Dumbness: If either of those teams succeeded, the entire Pokémon world would have been screwed forever. Covering the world in ocean could have destroyed human society, most of the human race, all Fire-type Pokémon worldwide, and a whole bunch of other species. Drying it up could have been even worse. All Water-types going extinct, a catastrophic increase in humidity, famine threatening mankind with extinction, and SO MUCH LESS WATER FOR EVERYONE (ya know, that thing all life needs TO LIVE), etc. There's not really an "upside" to either plan.
Pictured: Bad Idea.
The sheer thought that these maniacs were heavily supported is the scariest thing in the Pokémon franchise. After all, what moron would destroy the world out of tribute to bad Kevin Costner movies?
The Outcome: While both Legendary Pokémon awakened, Rayquaza - who's basically the ultimate dad of the Pokemon world - put them In their place, and both teams got disbanded. Which is another thing - there's a being whose sole purpose in existence is to stop Groudon and Kyogre from fighting each other - maybe you should make sure no one wakes it up? Send a couple of your minions to the Sky Pillar, just in case? Nah?
The Pokémon World is safe from eco-terrorists loving Dances With Wolves... for now.
Note: You know you're bad at this 'evil genius' thing when you end up on a list like this 3 times, Albert.
The Plan: S.T.A.R.S. survivor Chris Redfield is on a seemingly routine mission in Kijuju. A black market deal involving some giant monsters was about to go down. Along with his new partner, Sheva Alomar, he had to prevent the deal to make sure terrorists don't end up using those monsters for all sorts of terror stuff.
Along the way, some bad news emerged. The man behind the deal was Chris's old Captain Wesker. Not only that, he made a new virus, Uroboros, a bio-weapon so horrible it turns humans into hentai tentacle monsters. He already loaded that stuff into rockets and armed a bomber with those rockets. All he had to do was hop in that bomber, take off, and either fire the virus into civilian areas or wait for authorities to shoot him down. Either way, Uroboros would be released into the atmosphere, ensuring complete saturation of the globe or something like that.
Because 'Tentacle Monster Armageddon' sounded way too Japan.
The Dumbness: So... Wesker had the virus, the rockets, and the bomber. These are all the things he needed for his final solution. Just hop in, take, off, and bam, the entire human race got Wesker'd. Why make a deal with the terrorists at all, then? For more money? After Armageddon and the extinction of the human race, that money's not gonna be worth the paper it's printed on. Wesker had literally NO REASON to sell more B.O.W.s at that point. In fact, that deal caused all his problems. Without it, the BSAA would have never thought to send agents there, and Operation: Complete Global Saturation could have gone right on schedule.
I know what you're thinking. It's about Chris, right? Wesker wanted to be found, because he wanted to settle the score before turning everyone into a Japanese schoolgirl's worst nightmare. It actually sounds like something Wesker would do. It seems plausible. Except the game goes out of its way to make sure we KNOW that's not the case. Wesker was visibly surprised when he learned Chris is around. Also, previous encounters should have clued him in on how tough and resourceful Redfield is. It was obvious that underestimating him could come back to bite him in the ass later.
The Outcome: Chris and Sheva sabotaged the bomber, which fell into an erupting volcano, because at this point karma was very tired of Wesker's shit. He turned into a tentacle monster, got balls-deep in hot lava, and had his head blown off with two rocket launchers. Good job, idiot. No Resident Evil 6 for you!
But wait! That game sucked! So... was THAT the plan all along? To get himself killed before the series became horrible garbage? I take it back! I take everything back! Wesker, you've done it again, you magnificent bastard!