Like everybody. The more power one is given the more corrupt one becomes. It is the human nature.
I haven't found that at all. Having power reveals parts of a person's personality that aren't so evident in other situations. When you have no power you may supress parts of your personality to fit in or avoid trouble - with power, you no longer need to do that.
Healthy, decent, competant people tend to react pretty well to having power - it mostly makes them more responsible, not less (give someone a baby or small child to babysit and many if not most people will show a noticeably responsible and kind side).
But if someone's a jerk, or overwhelmed, or fundamentally doesn't respect others, then when they have power over others and no longer need to fake decency to avoid consequences, well, then you'll finally see those nasty parts of them.