You could let neutral people join as "apprentice evil-mongers", with a time-limit to start acting evil or get kicked out... you could make the leader be whoever's got the most evil score by the Gerakken Method (with some consideration for no. of games played), there's lots of things you could consider.
I hope you keep an evil theme, but, it makes things much more fun.
"In the left corner, we have the the original face of evil in the Metaverse, the ancient dragon of death and destruction, powerful as ever - ladies and gentleman, I present to you - GROSS!"
"And in the right corner, the vicious upstarts that have electrified the Metaverse with their promise of bringing 'the ultimate evil', I give you - THE EVIL EMPIRE!"
"Well, what do you think, Bob?"
"Call me crazy, Ray, but I think the Evil Empire can bring this one home."
"You are crazy."
"Hear me out! Sure, GROSS has some history of evil -"
"Some? Some? The Pirates' Book Of Evil Deeds has turned into a 20-volume encyclopedia!"
"Yes, but what have they done recently? No-one cares about the champions a decade ago, all they see is recent form, and the pirates haven't got any. They've gone corporate."
"Yes, but with a more efficient corporate structure, they've given themselves enough power to spread evil to a whole new level!"
"But what evil are they spreading? Piracy, smuggling, gambling, the occasional murder, they're all petty crimes. The Evil Empire's bringing a fresh message of evil, and it's really speaking volumes to the younger punters in the crowd."
"Sure, they talk big, but I haven't seen anything to justify their claims. They've done some depraved stuff, sure, but haven't we all? I know I've fire-bombed a few planets when I was pissed off, and I'm not calling myself the lord of evil. It's all about scale, they have to spread their evil over a million worlds like GROSS has done in the past before I take them seriously."
"GROSS spreads the message of evil to more planets, but they've lost the spirit of the message! They're fighting for the right to be evil, but they've forgotten what evil really means!"
"They don't talk about evil all the time cause they've already shown the Metaverse how much damage they can do. You don't need to see a mafia boss have someone killed every day to prove he can have it done!"
"I'm sorry, but I'm gonna have to disagree with you on this one. The purified evil of the Evil Empire shall triumph."
"We'll see who's standing after the fight."