My vote goes to Kratos of God of War. That dude kicks all kinds of ass. Before I played that game I would have gone with Zangief of SF2 fame. He kicked ass too.
I dunno, it seems like every game targeted at the 15-20 male demographic tried to out badass each other. This could be a loooong list.
My vote goes for the main character in Clive Barker’s Undying. Clive’s main contribution to the game was changing the main character from the ultra badass tattooed Count somebody or other into a swashbuckling Errol Flynn type. Who better to fight the undead?
Yuri Hyuga definitely has to be up there.
Kratos is pretty badass. I mean, he walks around with the ashes of his dead wife and son(who he murdered) permanently fused to his skin. And he kicks the ass of Ares, the god of war himself.
Zangief? The slow, tights-wearin’, oiled up guy who hung out in a mill surrounded by shouting men? Ken was more badass than him and he was a long-haired sailor.
Master Chief kicks some ass. Not at the level of having loved one grafted to him (then again I’ve yet to play Halo 2), but pretty badass.
Does Kefka from FFVI count? He destoryed the world. And he was insane, and he told off the good guys for moralizing before the final fight.
Kain from the Legacy of Kain series. That dude would seriously fuck you up.
Although…I may have to go with the 1985 Bears of Madden 2005. Da Bears!!
Shmeh. Kain just kills you. Raziel takes your SOUL!!!
What was the name of the old guy from Final Fantasy X, who was a samurai and kicked much ass? Was it Auron? If so, then Auron. If not, then that guy.
While we’re on the subject of Final Fantasy, Vincent from FFVII ought to be on the list too.
Kratos is a double hard bastard, but my vote goes to that character in Full Throttle. He had a voice like gravel and a chin of chisselled granite.
Ben, you mean?
“Little Mac” from Punch Out.
What? 
Thats him. Was a fun game for it’s time.
Ben gets my vote. Bad, badass.
[deadpan]“I fixed your door.”
::pause::
[deadpan]“It was sticky.”
or the ever popular: “I’m not putting my lips on that.”
Ben. Ben was great.
“You know what would look great on your face?”
“No, What?”
“The bar!”
“I need an escort”
“Does this look like an escort service to you?”
The Nameless One, from Planescape: Torment.
He keeps going and going and going…
Earthworm Jim
Just now I’m the middle of playing Destroy All Humans and the character in that, a little grey alien by the name of Crytosporidium, kicks some major ass. Especially as you progress in the game and upgrade your weapons and abilities. Right now I’m tossing tanks and giant robots around like they’re jelly beans and flattening city blocks with a blast from my saucer.
I’m sorry, but the most badass character is Tecmo Bo. Dude could take on the entire NFL and still run up the boards.