Here is the full list of all 66 Comit Legends achievements.
Beat Marathon Mode
Beat Comit the Astrodian
Beat Comit the Astrodian 2
Beat Comit the Astrodian 3
Beat Comit in Cosmo Knight's Revenge
Beat Comit in Krater Returns
Got your first Star Crystal
Unlocked Meta Comit
Beat Boss Rush Mode
Finished a Speed Run
Collect 100 Yellow Stars
Collect 1,000 Yellow Stars
Collect 10,000 Yellow Stars
Collect 5 Red Stars
Collect 50 Red Stars
Defeat 100 Enemies
Defeat 1,000 Enemies
Beat Planet Tropika
Beat Planet Magmo
Beat Planet Wave
Beat Planet Automata
Beat Planet Stormside
Beat Planet Frost
Beat Planet Sunburst
Beat Planet Sandpit
Beat Planet Cloud
Beat Starship Krater
Beat Planet Paradise
Beat Planet Aquatica
Beat Planet Mechanos
Beat Planet Party
Beat Planet Red
Beat Planet Blizzcicle
Beat Planet Dark
Beat Planet Starlight
Beat Planet Krater
Beat Planet Green
Beat Planet Speedway
Beat Planet Numbers
Beat Planet Inferno
Beat Planet Candy
Beat Planet Love
Beat Planet Grey
Beat Planet Odd
Beat Planet Gas
Beat Planet X
Beat Planet Berry
Beat Planet Cavern
Beat Planet Ooze
Beat Planet Castle
Beat Planet Fungus
Beat Planet Gold
Beat Planet Skyfall
Beat Planet Dusk
Beat Planet Tetra
Beat Planet Robotika
Beat Planet Tundra
Beat Planet Concrete
Beat Planet Neon City
Beat Planet Convoy
Beat Planet Crystal
Beat Planet UpDown
Beat Planet Bubbles
Beat Planet Pyramid
Beat Planet Keman
Beat Planet Chromatic