Here is the full list of all 15 GuardGrave achievements.
Complete World 1
Hit the bonus chest 10 times
Complete World 2
Complete World 3
Complete World 4
Complete World 5
Complete World 6
Complete World 7
Get 1,000,000 on a single playthrough
Finished the game on kids mode
Finished the game on Regular Mode
Finished the game on hard mode
Collect 25 bonus coins on a single playthrough
Give a ride to 3 enemies or more
Hit the final boss with at least 2 enemies on a lid