He could be as strong as Father would he reach his full potential. Darth Vader is not a force deity who can't destroy universe with the force. Thus, he didn't reach it.
What I'm saying is that we have 2 versions of the same character, and I'm not sure who's stronger(debatale).
Both are called Darth Vader, actually. 1)In the duel with Kenobi, 2)At the end of ROTJ
We don't have a version that is a force deity.
It looked like a ritual. And it was enviromental(circle).
He couldn't stop Son later.
That's correct, but that only proves that Vader is strong, not that he's stronger than Sidious.