i was playing as sadist, and there was a healer in my game making my power useless.do i get a new power?or do i just stay there uselessly

You can just get a new power because another alien is trumping yours. Yea sometimes it sucks. However, there is a technology card that lets you randomly select a new alien power in addition to your own. So if you play with the tech variant, at least you can have a chance that you may not get stuck with an unsuccessful power.

Tiz said:

Did you mean to say that you cannot get a new power if another alien is trumping yours?

You do not get a new power. That is part of Cosmic Encounter. Sometimes powers are made useless or less useful by other powers. You just have to try to win with a weakened power. I have been involved in many games in which the winner had a useless power or lost his power.