Here is the full list of all 14 Spelldash achievements.
Earn a platinum rune for the first time
Earn 10 platinum runes
Earn 25 platinum runes
Earn 40 platinum runes
WORLD-1 Completed
WORLD-2 Completed
WORLD-3 Completed
WORLD-4 Completed
Collecthathon Mode Completed
Challenge Mode Completed
Get 500 kills with fire spells
Get 500 kills with air spells
Get 500 kills with ice spells
Get 500 kills with lightning spells