It's hard being a protagonist. You make countless sacrifices, battle through countless levels, die countless deaths, and for all your hard work, you're still never going to be as cool as the villain. It's surprising how few goody-two-shoes ever make the transition to bad guy status and take advantage of its perks: cooler costume, army of minions, a chill flying death fortress to hang out in while those sucker heroes come to you.

But when they do, it's always a big event. We're talking about genuine good guys (playable protagonists) that somehow end up on the opposing side (antagonists that need to be taken down). Here's our list of the 8 greatest heroes-turned-villains in videogame history.

8. Alex Mercer (Good Guy: Prototype; Bad Guy: Prototype 2)

To be fair, whether or not Alex was ever "a good guy" is up for debate. He spends most of Prototype slicing & dicing anyone who has the misfortune to wander onscreen, and the rest of his time is occupied by learning new freakish nightmare powers in order to craft himself into a more efficient murder engine. Is it wrong to feel sorry for the enemies in a game? I'm hesitant to ask, because it feels like if Alex could reach out of the TV screen and kill the player, he would (I hear Radical Entertainment is working on that tech for the sequel). I wouldn't be surprised if the original idea for this game had you controlling the US military and was called The Story of the Horrible Monster No One Could Stop And Who Ate Everyone The End.

However, in the gap between developing Prototype and starting work on the sequel, apparently one Radical employee took a look at this walking wall of fleshy horrorblades and said "Hey, our hero looks way more like a Silent Hill villain than a protagonist. Let's just run with that angle." In Prototype 2, you'll be playing as a new character, a war veteran whose his wife & child were killed by Alex's rampage in the first game. Your new goal is the execution of your former main character. The working title? Prototype 2: You Deserve This.

7. Jumpman/Mario (Good Guy: Donkey Kong; Bad Guy: Donkey Kong Jr.)

Donkey Kong was a huge milestone in gaming, back when "having a cutscene" was a huge milestone in gaming. It even had a real storyline: a humble carpenter embarks on a quest to rescue his innocent girlfriend from the clutches of a renegade ape. Kids would line up at the arcade to take a crack at helping the heroic Jumpman rescue his damsel in distress. They thought they were fighting on the side of justice. They thought Jumpman just wanted his lady back. What they didn't know is that Jumpman just really f*cking hates gorillas.

In Donkey Kong Jr., suddenly the heroic everyman from the first game was flying his true flag: the pixelated middle finger of a big jerk antagonist. Not satisfied with merely winning his lady back, the newly-christened "Mario" had now locked Donkey Kong up in a cage and was siccing vicious animals on anyone who tried to free him, including DK's own son, Donkey Kong Jr.

It's possible that Mario, high off the victory and accolades of his first title, thought the audience would side with him in his weird mission to orphan a gorilla child. Or maybe PETA demanded a sequel proving how sympathetic giant apes could be. Either way, the Nintendo PR machine made sure Mario's image would never again be sullied by another psychotic anti-ape tirade.

6. Siegfried (Good Guy: Soul Edge; Bad Guy: Soul Calibur)

Siegfried started out as a major protagonist of Soul Edge, a wandering knight on a quest to slay the man who killed his father (turns out he had psychologically repressed the fact that the killer was him all along, but tragic heroes are always a little bonkers). Siegfried quested hard, fought valiantly, besting all manner of undead pirates, sexy ninjas, and creepy bondage freaks to reach the top.

Then he had to go and break the cardinal rule of any fantasy world – don't touch the cursed sword. Seriously. Hands off. You see a giant bloodshot eyeball peeking out at you from the hilt, you back away, understand? Hey, remember how it corrupted all who wielded it, carving a ragged, bleeding trail of pain and lamentation across half the world? For chrissakes, just read the game manual.

Apparently simple concepts like pattern recognition are foreign to Siegfried, because he doesn't hesitate to yoink that sword up and get corrupted like everyone else, becoming Nightmare, the main antagonist of Soul Calibur & its sequels. Well, at least he got a free giant claw arm out of the deal.