I'm going with the big rip for the end of the universe.

But I had cause to think of what the anti universe looks like.
Take the current universe and invert everything, what happens?

Matter is anti-matter ... not really that devastating if it is all the same kind in any universe.
Positive and negative charges are reversed as are beam currents.
Time runs backwards
Gravity is a repulsive force
Dark Energy is an attractive force, it shrinks spacetime.

Though I wonder if iron decays in the protons or if fission and fusion are reversed.