The only thing between you and your missing colleague are a few 100 different types of enemies.
If you can't beat them, then find a better weapon (among 100 different types).
If you're still having problems, discover and use weapon combos on them.
If they still stop you, transform into something better (like a zombie...werewolf...ghost.......).
If they stomp you, possess them and stomp their friends.
If they smash you, recruit them to fight back against their own kind.
If they continue to defeat you, find a secret path around them.
And if, after all this, you still can't win? Then saddle up on a giant Cassowary and show them who's boss.