The thing about Batman, to me, is that why do people like him so much? What makes him so appealing rather than Superman?
Well, I think the truth is rather sad and unfortunate. People, I think, like Batman on a subconscious level because he operates almost exactly like a villain would. In fact, if he WERE a villain, he'd probably operate much in the same way he does now, but would, you know, kill instead. He'd still have a secret lair, he'd still have sidekicks (henchmen), and he'd have it all be secret as he hides behind the mask of poor orphaned Bruce Wayne, Prince of Gotham. Hell, if we consider his ability to raise an army from The Dark Knight Returns (where he creates the Sons of Batman from the Mutants), then he wouldn't even NEED to do everything on his own...but he would. He'd raise hell. In fact, he'd probably be a better villain than hero, because he'd be actively trying to dismantle the system rather than preserve it as well as others in danger. Think about it: Batman exploring Gotham City Police Department one night. Who's gonna stop him? Commissioner Gordon? He could tear Gotham apart, and it's rather terrifying.
And when you think about how much he could easily fuck up the city he protects, you start to see why he's a formidable foe in general. He is DANGEROUS. He's unpredictable if he has no restrictions other than his training. He could get away with just about anything. He has the skills, he has the money, and he has the mind, body, training, skills, education...it's all right at his fucking fingertips.
But who'd stop him? Who'd let him get away with this?
Well, one person: Alfred. The only fucking problem is that GOD DAMN ALFRED is too fucking based to let that shit happen. He'd turn Bruce in. He'd do the right thing. But...if Batman had an EVIL Alfred? You best run the fuck away. But really, all he'd need is a loyal companion like Alfred, but evil. Someone like Mercy for Lex Luthor.
In conclusion, no evil Alfred = no evil Bats