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