Here is the full list of all 99 3 Minute Heroes achievements.
Clear round 6 with Zealot as main hero
Defeat Bluebe.
Defeat Bluebe before round ends.
Obtain 100 gems.
Clear round 6 with Sorcerer as main hero
Defeat Pomegrana.
Defeat Pomegrana before round ends.
Get level 2 gem in upgrade tab for the first time.
Defeat Broccol.
Open Invasion mode
Obtain 1000 gems.
Obtain 10000 gems.
Get level 3 gem in upgrade tab for the first time.
Get level 4 gem in upgrade tab for the first time.
Get level 4 gems in all three slots in upgrade tab.
Obtain 10 flags.
Obtain 50 flags.
Obtain 100 flags.
Obtain all flags.
Obtain 10 crowns.
Obtain 50 crowns.
Obtain 100 crowns.
Obtain all crowns.
Defeat Avoca.
Defeat Toma.
Clear round 12 with Sorcerer as main hero
Clear round 12 with Sorcerer as main hero with all friends
Clear round 6 with Warrior as main hero
Clear round 12 with Warrior as main hero
Clear round 12 with Warrior as main hero with all friends
Clear round 6 with Hunter as main hero
Clear round 12 with Hunter as main hero
Clear round 12 with Hunter as main hero with all friends
Clear round 6 with Farmer as main hero
Clear round 12 with Farmer as main hero
Clear round 12 with Farmer as main hero with all friends
Clear round 6 with Paladin as main hero
Clear round 12 with Paladin as main hero
Clear round 12 with Paladin as main hero with all friends
Clear round 6 with Oracle as main hero
Clear round 12 with Oracle as main hero
Clear round 12 with Oracle as main hero with all friends
Clear round 6 with Barbarian as main hero
Clear round 12 with Barbarian as main hero
Clear round 12 with Barbarian as main hero with all friends
Clear round 6 with Inventor as main hero
Clear round 12 with Inventor as main hero
Clear round 12 with Inventor as main hero with all friends
Clear round 6 with Bartender as main hero
Clear round 12 with Bartender as main hero
Clear round 12 with Bartender as main hero with all friends
Clear round 6 with Priest as main hero
Clear round 12 with Priest as main hero
Clear round 12 with Priest as main hero with all friends
Clear round 6 with Rogue as main hero
Clear round 12 with Rogue as main hero
Clear round 12 with Rogue as main hero with all friends
Clear round 6 with Alchemist as main hero
Clear round 12 with Alchemist as main hero
Clear round 12 with Alchemist as main hero with all friends
Clear round 6 with Gambler as main hero
Clear round 12 with Gambler as main hero
Clear round 12 with Gambler as main hero with all friends
Clear round 6 with Plague Doctor as main hero
Clear round 12 with Plague Doctor as main hero
Clear round 12 with Plague Doctor as main hero with all friends
Clear round 6 with Vampire as main hero
Clear round 12 with Vampire as main hero
Clear round 12 with Vampire as main hero with all friends
Clear round 6 with Treasure Hunter as main hero
Clear round 12 with Treasure Hunter as main hero
Clear round 12 with Treasure Hunter as main hero with all friends
Clear round 6 with Fisherman as main hero
Clear round 12 with Fisherman as main hero
Clear round 12 with Fisherman as main hero with all friends
Clear round 6 with Merchant as main hero
Clear round 12 with Merchant as main hero
Clear round 12 with Merchant as main hero with all friends
Clear round 12 with Zealot as main hero
Clear round 12 with Zealot as main hero with all friends
Clear round 6 with Warlock as main hero
Clear round 12 with Warlock as main hero
Clear round 12 with Warlock as main hero with all friends
Clear Invasion 1
Clear Invasion 2
Clear Invasion 3
Clear Invasion 4
Clear Invasion 5
Clear Invasion 6
Clear Invasion 7
Clear Invasion 8
Clear Invasion 9
Clear Invasion 10
Defeat Acumina.
Defeat Avoca before round ends.
Defeat Toma before round ends.
Defeat Broccol before round ends.
Defeat Acumina before round ends.
Defeat every mascot boss before round ends.