Depends, if we go only with traditonal light side Jedi, then that means Luke and his band of Jedi are excluded.
In my opinion with supoorted logic, is that Luke is moreso of a Grey Jedi, he uses both the Dark Side and Light Side. His offensive capabilities are often the reason he defeats extremely diffcult opponents.
Inclusive of NJO and DN, Luke outclasses everyone.
Exclusive of NJO and DN, i'm inclined to say Yoda, but perhaps the Jedi Masters in TOTJ and KOTOR may defeat him.
In my opinion with supoorted logic, is that Luke is moreso of a Grey Jedi, he uses both the Dark Side and Light Side. His offensive capabilities are often the reason he defeats extremely diffcult opponents.
That might have been the case for the Unifying force...
The Unifying Force was the in-between version of the Old Jedi philosophy and Vergere's philosophy they temporarily settled on at the end of the New Jedi Order. Essentially, it says there is a Dark Side but it wasn't natural and was created by people using the Force for evil. It also says that you can use the Dark Side for good without reprocussion.
( Spoilers for Dark Nest )
Spoiler:
Luke later decides this theory is innacurate when he realizes that even in calling on the Dark Side for good it's twisting him physically and mentally.