Here is the full list of all 20 John The Zombie achievements.
Eat 50 brains.
Eat 30 brains.
Eat 10 brains.
Kill 20 zombies with a car.
Learn 5 skills.
Learn 10 skills.
No agressions for 10 minutes.
Win the first race.
Win the second race.
Win the third race.
Attack 5 cops.
Catch one big fish.
Score 50 points in basketball.
Finish the campaign.
Eat 10 cow's brains.
Win the first horse challenge.
Win the second horse challenge.
Score 500 points by causing chaos.
Score 1000 points by causing chaos.
Score 2000 points by causing chaos.