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