Here is the full list of all 24 Idle Monster TD achievements.
Defeat 1,000 bosses.
Reach 1 day of in-game play time.
Participate in 1 PvP Tournament.
Pass wave 100.
Defeat 10,000 enemies.
Unlock 10 unique monsters.
Prestige 1 time.
Pass wave 1000.
Pass wave 5000.
Prestige 25 times.
Prestige 100 times.
Unlock 25 unique monsters.
Unlock all 44 unique monsters.
Defeat 1,000,000 enemies.
Defeat 10,000,000 enemies.
Defeat 10,000 bosses.
Defeat 100,000 bosses.
Reach 10 days of in-game play time.
Reach 25 days of in-game play time.
Participate in 5 PvP Tournaments.
Participate in 12 PvP Tournaments.
Have a monster reach Ascension level 1.
Have a monster reach Ascension level 5.
Have a monster reach Ascension level 15.