@The_Tempest
Darth Sidious is much more likely to be hyped as an untouchable along with Luke Skywalker in comparison to any other character, I have noticed this trend since I have joined this form. Few have considered the possibility that these two have competition from ancient era and can be defeated.
As for Emperor Vitiate:
He performed badly against Hero of Tython because he was vulnerable after the disruption of his super-ritual. It really took a toll on him for a while and he still managed to put up a reasonable fight, even destroyed a portion of Dark Temple in an effort to kill the opponents.
Anyways, member DarthAnt66 is correct that Emperor Vitiate continues to grow in power seemingly endlessly in part due to his Force Drain related actions and also due to his condition. He is virtually unstoppable in power progression aspect and would eventually reach a point that he would consume the entire galaxy if his essence is not undone. Though how his essence will be undone remains to be seen.
So far, The Ones are the latest addition to no-limits-fallacy rule.