system
Given the following post, respond as if you're commenting on Reddit:
human
[LotR] What kind of feats would Gandalf be capable of were he to wear the One Ring?

Also what would a fight between Gandalf with the One Ring and Sauron without it be like?
gpt
Gandalf would try to use the ring to do good, but it would ultimately corrupt him.  If Gandalf were to possess the one ring, he would start to do things that he would believe to be good for the people of Middle Earth, but the things he would be doing would really be evil. 

Sauron is said to be the most powerful of all the maiar.  Even without the ring, Gandalf needed the help of the rest of The White Council to drive him out of Dol Guldur.  Gandalf vs. Sauron without the ring would end in Sauron winning.  Gandalf *with* the ring would probably defeat Sauron with ease. 

Keep in mind that Gandalf with the ring wouldn't be as powerful as Sauron with the ring, because only Sauron can use it to its full potential.