Here is the full list of all 12 Kill the Bad Guy trophies - there are 8 bronze, 3 silver and 1 gold.
Cut off 5 heads
Make the Bad Guy run 5000 meters
Finish Level T666
Kill a Bodyguard
Finish Level DNKTBG
Finish Level Zombies!
Get 60 passports
Spill 100 liters of blood
Kill the Bad Guy 25 times
Put a dog on a catapult
Kill the Bad Guy 5 times as he's escaping
Commit your first assassination