It is said that power corrupts and absolute power corrupts absolutely.
Have you ever looked at this notion in a Champions campaign? Many superpowered sorts gained their powers suddenly, without any time to mentally prepare to deal with it, yet they emerge as heroes.
Why is this so?
What drives a person who gains powers to act with such selflessness?
Have they ever been tempted to use their powers to make their own lives better or indulge a desire?
For example, consider a mentalist with powers of telepathy, mind control, etc. If he sees a beautiful woman on the street, is there a temptation to use those powers on her? Even just using telepathy would give a boost to an attempt at seduction, let alone something more crude like mind control or emotion control.
Is the corruption of power a theme you've explored in a campaign, either as a player or GM? How did it work out?