1. Make zombies respawn endlessly through the windows. 2. Zombies cannot die, but can be temporarily knocked out/down. Basically similar to Mr. X 3. Immune to head exploding, but other parts are still fair game. 4. More aggressive (they move more quickly) and able to move out of their safe zones. 5. Zombies are more quickly to be aware of you. 6. Lickers will attack ANYTHING that moves. Walking slowly will still keep you unnoticed. 7. Mr. X has no weakness and cannot be knocked down. 8. Mr. X no longer punches you. He'll just grab you and crush your head. To avoid this; grenade, flash g., knife is your only escape.