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