Here is the full list of all 39 Mega Veg Man achievements.
Fail 200 times
Fail 20 times
Fail for the first time
Complete any level
Complete world 0
Complete World 1
Defeat The Great Flea
Complete World 2
Defeat The Devourer
Complete World 3
Deafeat The Fungi 5
Complete World 4
Escaped The Ghost
Complete World 5
Defeat The Frostbite Knight
Complete The End
Defeated Doctor Hopps
Obtained a gold tropy on any level
Earn every gold trophy in every world
Complete an entire world without failing once
Earn every achievement
Bonk 20 enemies
Bonk 60 enemies
Bonk 100 enemies
Changed your costume
Collect all costumes
Consume 10 apples
Consume 50 apples
Consume 15 lollipops
Complete Vegan Mode
Complete Vegan mode within 2 hours
Discover the spider cave
Unlocked Party setting
Dig up a relic of the past
Unlocked Fossilized setting
Complete Malnourished mode
Complete Boss Rush
Released the spirit within the ancient tomb
Discover Geode world