Here is the full list of all 27 Arena Hero achievements.
Discover 40 unique items.
Complete the silver league.
Complete the chaotic bronze league.
Reach hero level 60.
Complete a chaotic arena.
Reach hero level 40.
Reach hero level 20.
Discover20 Unique items.
Wear a tier 2 armor set.
Defeat a Legendary enemy.
Complete the bronze league.
Defeat a boss.
Discover 10 unique items.
Defeat a champion enemy.
Complete the chaotic silver league.
Complete the gold league.
Complete the chaotic gold league.
Complete the champion's league.
Complete the chaotic champion's league.
Have 5 enhancers equipped.
Have 7 tier 3 items equipped.
Reach hero level 80.
Reach hero level 100.
Discover 60 unique items.
Discover 80 unique items.
Bounce 3 times off the air.
Defeat the slime king without attacking it.