ER apparently possessed god-like power, but as noted didn't do much.
What we do know,
is that he definitively had the power to revert the 616 universe back to it's pre-Big Bang point,
even before the concept of "nothingness" came into play.
That's pretty uber, to implode all of 616's history.
We know this is factual due to the reaction of the hierarchy.
Especially observe 'Oblivion' literally shivering in fear after ER's threat,
signifying to us that ER was able to do it, and it seemed easily at that.
What's ER's cap level though? Who the hell knows.