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human
[Star Wars] How powerful is Luke compared to prequel Jedi?

Is he just assumed to be the most powerful Jedi of all time because all the other Jedi were wiped out? How would he stand in a fight against Mace Windu or Anakin?
gpt
Largely depends on the timeframe and canon. During time of the movies, he isn't exactly an epitome of might - while he did defeat Darth Vader, the Palpatine went down only due to very specific circumstances that didn't rely on Luke's power in the Force or with a lightsaber. He probably wouldn't stack up very high in the Prequel-era Order, he's alright, but much work needs to be done with his training. 

Now, post-Endor, Luke actually had time to work on his self-education. While new canon info is scarce, it seems that in both canons he travelled the galaxy uncovering the lost jedi lore and teachings. So by the time Luke trains his new Jedi Order he's a legit Jedi Master, who probably won't go down without a fight against Windu or young Anakin. 

By the time he is so-called "Grandmaster" Luke, he essentially learned nearly all there is to learn about the Force, and more or less living repository of Jedi lore. At this point it's better not even try to fight him, since he probably already learned an obscure power specifically for this occasion.