Source: comicvine.gamespot.com

6. Superior Spider-Man

I guess this one technically counts?

I mean, it was the real Spider-Man's body; it just wasn’t his mind. For you see, a dying Doctor Octopus used his final act to transfer his brain into Spider-Man's body. He took over the hero, but was humbled when he was flooded with memories of the events that made Peter a good guy. He decided he would be a superhero, but he would do it his way.

This basically meant he was a giant a-hole who literally recruited henchmen. He superheroed the way most people supervillained. And he tried to pull a lot of creepy stuff with the people in Peter Parker's life.

The Superior Spider-Man wasn't explicitly evil, but he was definitely morally skewed, beating villains within an inch of their lives if they looked at him funny. He eventually gave up his foothold in Spider-Man's mind when he realized that Peter was the better hero. He then faded away and went full-on supervillain again.

                             
                            Source: berkeleyplaceblog.com

5. Iron Man 2020

Arno Stark, Iron Man 2020. Man, maybe they should have set that date a little further in the future, huh? Like, this character will be dated before my car's next service appointment.

I adore the Iron Man 2020 armor. It was so malevolent by design. It had teeth!! And a glower! And those huge gear things on the shoulders were so great, and so deeply silly. They must cut down on mobility, and they're definitely hell on air resistance. It would be the first Google Images result for How do I make the Iron Man suit look very evil?

Arno was a descendent of Tony Stark who decided he wanted to use his ancestor's technology to take over the world and be evil and stuff. You know, the basics.

He attempted to fight Tony on numerous time-travel occasions, but despite having a more technologically advanced suit of armor, he wasn’t as skilled with it and lost repeatedly.