Here's the list of all the monster abilities, updated:
Spooky Space Kook: Spawns with Energy Fields around the map that will slow you down while inside them.
The Creeper: Teleports around the map to ambush you after losing sight of you for the first time.
Captain Cutler: Covers Clue spawn points in seaweed. You won't know what's under it until you remove it.
Green Ghost: Is cloaked until he spots you.
The Witch and the Zombie: Forces you to capture both enemies.
The Black Knight: Charges at you in an attempt to impale and kill you.
Snow Ghost: Roars and shakes your camera sometimes when a chase begins.
Witch Doctor: Has a statue that always knows where you are, and will relentlessly pursue you in an attempt to kill you.
The Tar Monster: Covers random pathways in Tar piles.
Charlie the Robot: Is the fastest enemy in the game.
The Sea Monster: Will spawn with fish piles around the map, which he will use to ambush you when you walk near them.
The Ghost Clown: Can't be seen from a certain distance.
The Actor: Changes disguises with each clue obtained, and forces you to try to capture him 3 times.
Captain Moody: Lays beartraps down, and can't be heard when roaming.
The Beast of Bottomless Lake: Instead of sprinting at you, he will pounce at you, most likely resulting in death if he is too close.