Lawful Evil is my favorite Evil.

You don't have to do evil things all the time, or really ever if it isn't called for. You set a goal or an ideal and you go out to accomplish it. The difference between Lawful Evil and the good alignments is what you'd do to accomplish those goals or ideals. Where Chaotic Evil is generally hard to hide, you could have someone Lawful Evil in the party and if no one stands in the way of what they think is necessary they might not even do anything morally wrong.