You can say he is the end of all thing or embodiment of death but neither of those is actually him but just human language attempted it best to describe him.
If we try to describe his power, it's somewhat like omni-negation where he can deny the state of existing of everything he wants including concepts.
However, his power is far more than omni-negation because it works instantaneously, it violates causality (hence time ability and causal abilities are worthless against it), lastly, he is the one who defines what is the definition of existing and what is the definition of cease from existing so that his power could work.
In short, his power is beyond the logic of humanity and requires a transcending understanding of duality (such as existing and non-existing/ light and darkness/ nothing and something) to grasp it. It is sort of omnipotent because omnipotent is contradicting itself and is a paradox yet even when it is contradicting itself it is absolutely logical for contradicting itself.