Vader power Level was higher they he himself knew about.
Luke made him stronger then he ever could be being a father would do that to you.
I would love to expound on the growth of jedi and the jedi order...
From what ive read personally before disney made alot of shyt non canon (which idgaf about cuz the star wars eu and old republic shyt was literally some of the best stuff they had)
As far as the force, goes it was
Anakin >>>>>>>>>>>>>>>>>>>Palpatine
But when he lost his limbs to Obi Wan while at the same time becoming a Baby Sith instead of Jedi Knight/Master it reset his power as
Palpatine >>>>> Vader
Palp was strong enough in the force to keep a young, still confused and angry, demoralized and recently crippled Vader in line but that was also psychological.
When Vader got OLDER, he regained SOME of his former power, not all of it, but alot, and his light saber skills became DEADLY. If he really wanted to by the time of Empire he couldve taken out Palp but he was literally obsessive, first with hunting down the remaining Jedi, then with hunting down Luke