Here is the full list of all 24 Tunche: Arena achievements.
Air juggle the frog plushie 5 times.
Defeat 75 monkeys in total.
Defeat 30 trunks in total.
Defeat 10 giant frogs in total.
Defeat Boutu in Horde mode.
Defeat 50 peccaries in total.
Defeat 200 frogs in total.
Defeat one enemy of each type.
Reach S combo style.
Buy a skill in Endless mode.
Complete a Wave in Endless mode.
Clear a Wave without getting hit.
Access any of the Leaderboards.
Choose a reward in Horde mode.
Defeat Boutu in Horde mode without being damaged.
Reach Wave 50 in Endless mode.
Get a total of 50 S, SS or SSS kills in Endless mode.
Beat Horde mode without having chosen any reward.
Beat Horde mode without having spent XP on the Skill Tree.
Reach SS combo style.
Reach SSS combo style.
Use all the skills.
Annoy the Skill Tree guy