It's too bad but the amount of manga that falls into this category is very little. Pumpkin Scissors is worth a try, though I'm not sure if he's "scary" enough for you.
I'll throw this one in too, even though it got axed at the most interesting part so it's a little disappointing. Had soo much promise, sigh... anyway, Dark Mage has a deformed main character. Read it if you're bored or something.