Just played a two player game (Medics and Command).
In the middle of the third wave (round 8), the Medics (mostly their Ajax suit and some Stim Packs) had everything cleaned up already with two healthy Field Medics and some gear left over, while Command was on the last enemy with three troops left. Things were looking good, until...
Reveal: Swarm Caller (couldn't kill it, so...)
Reveal: Swarm Caller (couldn't kill it either, so...)
Reveal: Eater of Hope (that one ate the rest of my troops, but at least had the decency to die with them)
Reveal: Bomber (Base had 10 hp left)
...and there was another enemy unrevealed behind it, too.