Here is the full list of all 66 Mech League Hunting achievements.
Complete Story Mission 1
Complete Story Mission 2
Complete Story Mission 3
Complete Story Mission 4
Complete Story Mission 5
Complete Story Mission 6
Complete Story Mission 7
Complete Story Mission 8
Complete Story Mission 9
Complete Story Mission 10
Complete Story Mission 11
Complete Story Mission 12
Complete Story Mission 13
Complete Story Mission 14
Complete Story Mission 15
Complete Story Mission 16
Complete Story Mission 17
Complete Story Mission 18
Complete Story Mission 19
Complete Story Mission 20
Complete Story Mission 21
Destroy 10 Beetles
Destroy 50 Beetles
Destroy 100 Beetles
Destroy 50 Troopers
Destroy 200 Troopers
Destroy 500 Troopers
Destroy 50 Bombarders
Destroy 100 Bombarders
Destroy 200 Bombarders
Destroy 10 Captain Troopers
Destroy 50 Captain Troopers
Destroy 100 Captain Troopers
Defeat Daqraq 3 times
Defeat Daqraq 10 times
Defeat Daqraq 25 times
Destroy 50 Flies
Destroy 100 Flies
Destroy 500 Flies
Destroy 50 Flying Harpies
Destroy 200 Flying Harpies
Destroy 500 Flying Harpies
Destroy 50 Flying Troopers
Destroy 200 Flying Troopers
Destroy 500 Flying Troopers
Destroy 50 Harpies
Destroy 200 Harpies
Destroy 500 Harpies
Destroy 50 Kamikaze Wasps
Destroy 100 Kamikaze Wasps
Destroy 200 Kamikaze Wasps
Destroy 10 Mantis
Destroy 50 Mantis
Destroy 100 Mantis
Defeat the Megataur 3 times
Defeat the Megataur 10 times
Defeat the Megataur 25 times
Destroy 50 Minitaurs
Destroy 100 Minitaurs
Destroy 500 Minitaurs
Destroy 10 Minotaurs
Destroy 50 Minotaurs
Destroy 100 Minotaurs
Destroy 50 Spiders
Destroy 200 Spiders
Destroy 500 Spiders