Strongest fictional force in the universe? war time

The Zerg Swarm

The Necrons

The Borg

The Demons and Stroggs

The Divine Order of the league of 20,000 planets

The Flood

The Combine

The Tyranids

The Empire

The Burning Legion

or something not on the list?

no super god-like characters like galactus from the marvel comics or goku from dbz plZ=)

Realistically speaking, I think the flood. It depends what what immune defences the other species have, but the Flood can take over anything that is sentient.

Assuming they have a hive-mind nearby, they can also be pretty mobile and dangerous, especially in numbers.

My second guess would go to the Zerg.

who needs an army when you have a guy who can eat planets like you and me eat doughnuts

im talking about galactus