Here is the full list of all 25 Mitch: Berry Challenge achievements.
Unlock all the achievements
Complete the game
Beat the final Boss
Beat over 45 Biturus during the final boss battle
Find all the Blackberries, Complete all levels without using health backups and Get all the Golden Clocks
Unlock all Iguanas in Singleplayer
Unlock all the golden clocks
All blackberries collected!
Complete all levels without using health backups
Play 50 local multiplayer matches
Complete Level 22
Collect Over 3000 Yellow Berries
Complete Level 21
Complete Level 19 without receiving any damage
Complete 18 levels without using health backups
Beat the first boss
Complete the first 17 levels
Beat 100 Biturus
Complete Level 9 without receiving any damage
Complete Level 6 without receiving any damage
Beat 100 Enemies
Complete 5 levels without using health backups
Beat your first Bituru
Complete a level unlocking a golden clock for the first time
Grab your first blackberry