In terms of being immediately lethal, probably the first one, since the gravitational effects Meta Gravity Manipulation can produce can affect even beings outside of spacetime, in metaphysical/conceptual planes, etc, and Meta Power Negation can negate any power that might be used to escape/resist it, if that were even possible.

However, 'extremely powerful' and 'lethal' in a more general sense? I would say the second one. Admittedly, Causality Reversal is a bit dwarfed by Boundless Inner World, since the latter is an absolute power and the former can't really do much to beings that transcend/manipulate causality. When it comes to Boundless Inner World, the user is virtually omnipotent over it, capable of anything within it or involving it, and so anything that ends up in there has automatically lost. They are also able to externalise their world out, so its not like you can just avoid going into their world (they can also just internalise you into their world for the same effect). They can also create powers for themselves in their world, or create Inner Gods (with any capabilities they want) that can act on their behalf to affect the outer world, or that they can channel the powers of, that will always be completely loyal to them.

The third... like I have said before, I think infinity is a bit dwarfed by absolutes, and a pure and immaculate world isn't particularly lethal or powerful, at least compared to the other powers here.