Just so you don't miss it, there are four parts above to my response, with some other posters making posts in-between.
Part 1: Luke's duel with Sidious / Luke's potential
Part 2: Luke's duel with Sidious / Luke's potential
Part 3 (brief): How close the duel was and Byss as a nexus
Part 4 (somewhat brief): feats
Have briefly skimmed over the arguments.
Don't wanna interrupt but, DE Luke was having his potential (twice of ROTJ Sidious, so perhaps close to or greater than DE Sidious) unlocked. So in that specific instance he was aided by an external factor that unlocked force potential into actualised power. This is perhaps similar to how Mortis unlocked Anakin's true potential which allowed him to ragdoll the children simultaneously. So Luke's win is sort of irrelevant.
Originally posted by LordOfTheLight
In fact, if anything, the whole "Abeloth" arc, only reinforces Luke's potential being comparable to Anakin's.
Comparable and the same are two different words.
Anakin is the chosen one. He was conceived by the force, and only he was destined to replace the father. Luke is comparable, but not the chosen one.
Originally posted by samappoYou should deal in actual power. Vader's superior force power and dueling skills netted him an L to Kenobi. I don't care what you're capable of I care more about what you do in the heat of fair combat.
That's a straw man. We are talking about force potential, not actualised power.
Also to further clarify that Byss was benefiting Palpatine more (credit to a poster who can reveal themselves if they want to):
The Emperor's throneworld had an elegance to it that went far beyond the staid, bueraucratic monotony of Coruscant's blanketing city. But beyond the world's beauty, that radiated the dark side, a fitting place for the Emperor to stage his return to power.****
Despite his clone's rapid deterioration, Palpatine seemed invulnerable on Byss, and his use of Force powers was more of an afterthought than an exercise.
****
Luke Skywalker traveled to Byss in search of the dark power that called to him from across the galaxy, and found the resurrected Emperor Palpatine. Within Palpatine's lair, and surrounded by the dark side pall that covered the planet, Luke could not stand against the Emperor.
- Dark Empire Handbook