Here is the full list of all 29 Mighty Party achievements.
Open 5000 chests
Win 500 battles in PvP with Trixy
Achieve 200 rank
Win 500 battles in PvP with All-Father
Reborn units 20 times
Open 2500 chests
Sacrifice units 100 times
Achieve 100 rank
Achieve 1 league
Win 500 battles in PvP with Son of Woods
Reborn units 1 time
Achieve 5 league
Achieve 50 rank
Achieve 10 league
Open 500 chests
Invite 10 friends
Win 1 battle in Divine Arena
Open legendary chest
Win 1 battle in Survival
Achieve 20 league
Sacrifice units 1 time
Invite 1 friend
Open 50 chests
Complete Chapter 3 in Journey
Achieve 10 rank
Complete the tutorial
Defeat first boss in Journey
Open epic chest
Win 1 battle in PvP