Here is the full list of all 51 MMA Arena achievements.
Complete Tutorial
Reach Level 5
Reach Level 10
Reach Level 15
Reach Level 20
Reach Level 30
Reach Max Level
Unlock a 3rd martial art
Get one Red Belt
Get two Red Belts
Get one Blue Belt
Get two Blue Belts
Get one Brown Belt
Get two Brown Belts
Get one Green Belt
Get two Green Belts
Get one Orange Belt
Get two Orange Belts
Get one Yellow Belt
Get two Yellow Belts
Get one Purple Belt
Get two Purple Belts
Get one Black Belt
Get two Black Belts
Get three Black Belts
Buy ten items from the shop
Buy twenty items from the shop
Buy fifty items from the shop
Win a match with a KO
Win five matches with a KO
Win ten matches with a KO
Win twenty matches with a KO
Win thirty matches with a KO
Earn 50.000 coins
Earn 200.000 coins
Earn 500.000 coins
Earn 1.000.000 coins
Create a second fighter
Create a third fighter
Create a fourth fighter
Create a fifth fighter
Complete 25% of MMA Career
Complete 50% of MMA Career
Complete 75% of MMA Career
Complete 100% of MMA Career
Play ten critical cards
Play twenty critical cards
Play fifty critical cards
Play 10 Combos cards
Play 20 Combos cards
Play 50 Combos cards