bad guys in this are technically not zombies, but they might as
well be, since they resemble zombies. In this game, humans are
hosts to parasites.
first, these bad guys look like regular zombies, but once you
attack them, the head and spine jumps out - at least as far as
the Nazi soldiers who are infected are concerned. The head will
jump about on the spine, chasing you around.
the swamp level of the game, your enemeis - humans who were once
citizens of the swamp area - are more mutated in nature, as some
have very long arms or deformed hands. Also in the swamp level,
you'll meet up with big spider-looking monsters.
other points in the game, you'll be confronted with Nazi soldiers
who wear masks and who can fly because they wear jet packs. Personally,
I find them creepy, so you'll find an image of one below.