Picard: Power corrupts.
Riker: And absolute power corrupts absolutely.
Ok, so what do you call this Galaxy Class Starship that has the power to beam people in and out of existence, re-create any object, setting or life form from any planet, ship or station from any time, create it's own life form, and pulverize an entire solar system with it's heavy armaments? Having that power is ok, but having the power to bring a dead girl back to life? You're worse than Satan.
Q's power is significantly more than any of that, any of anything, ever. What's the worst that could happen? Riker could end up like Q. The horror!