My brother was playing the "token Evil guy" in a party of mostly Good PCs. As many threads attest, this can often go very wrong.
Instead, he made him "functionally" Evil.
He rolled a 3 for Charisma and it was 3.5 FR so he had regional feats to choose from. So he built a Lawful Evil Human Monk, scarred at birth by goblinoids that had tried to burn his home down with him in it after they murdered his family.
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He picked the regional feat that gave him a bonus to killing goblinoids. And his primary purpose in life was to protect other races against "the goblinoid threat".
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So he would viciously murder any goblins, hobs, or bugbears he could get his hands on and was generally a one-word-answer kind of guy when people talked to him. But he had no animosity at all towards other races or his fellow PCs. He would offer his opinion on the best (usually the most effective and brutally efficient) way to do something, but was content to respect the party's wishes when it came to getting things done.