Your villain should be committed to her or his cause, just like the heroes. Your villain should be convinced that she or he is right, and have reasonable justifications for her or his behavior.
Your villain should inspire others to follow the same cause, just like the heroes.
Your villain should be willing to do anything to accomplish her or his goals. Murder, theft, bribery, kidnapping; all of it is defensible in pursuit of a goal. The villain may not relish taking those actions, but the villain must be willing to take those actions.