Here is the full list of all 60 Park Rangers of The Undead achievements.
Slay 100 Glutton Zombies
Slay the secret boss
Beat Arena Wave 15 (Desert)
Slay 150 Chicken Zombies
Slay 500 Soldier Zombies
Slay 50 Glutton Zombies
Beat Arena Wave 14 (Desert)
Slay 500 Medic Zombies
Beat Arena Wave 13 (Desert)
Slay 100 Chicken Zombies
Beat Arena Wave 12 (Desert)
Beat Arena Wave 11 (Desert)
Slay 1000 Heavy Zombies
Beat Arena Wave 10 (Desert)
Beat Arena Wave 9 (Desert)
Beat Arena Wave 8 (Desert)
Beat Arena Wave 7 (Desert)
Beat Arena Wave 6 (Desert)
Beat Arena Wave 5 (Desert)
Beat Arena Wave 4 (Desert)
Slay 1000 Rat Zombies
Beat Arena Wave 3 (Desert)
Slay 1000 Dum Dum Zombies
Beat Arena Wave 2 (Desert)
Beat Arena Wave 1 (Desert)
Beat Arena Wave 15 (Forest)
Slay the Gunner boss
Slay 250 Soldier Zombies
Slay 25 Glutton Zombies
Earn $1.000.000
Slay 250 Medic Zombies
Beat Arena Wave 14 (Forest)
Slay 50 Chicken Zombies
Beat Arena Wave 13 (Forest)
Slay 500 Heavy Zombies
Beat Arena Wave 12 (Forest)
Slay 100 Soldier Zombies
Beat Arena Wave 11 (Forest)
Slay 100 Medic Zombies
Beat Arena Wave 10 (Forest)
Slay the Tank Zombie boss
Slay 250 Heavy Zombies
Beat Arena Wave 9 (Forest)
Beat Arena Wave 8 (Forest)
Slay 500 Rat Zombies
Slay 500 Dum Dum Zombies
Beat Arena Wave 7 (Forest)
Beat Arena Wave 6 (Forest)
Beat Arena Wave 5 (Forest)
Slay the Big Bad boss
Slay 250 Rat Zombies
Slay 250 Dum Dum Zombies
Earn $100.000
Beat Arena Wave 4 (Forest)
Beat Arena Wave 3 (Forest)
Beat Arena Wave 2 (Forest)
Complete the Training Course with a perfect score in 40 seconds or less.
Complete the Training Course.
Beat Arena Wave 1 (Forest)
Earn $10.000.000