Here is the full list of all 19 Sproggiwood achievements.
Defeat Surma on Easy.
Defeat Surma on Normal.
Kill a bizarro cloghead.
Kill a monster that loves you.
Kill 5 enemies in one turn.
Defeat Big Ick on Normal.
Defeat Big Ick on Easy.
Kill 10 enemies in one turn.
Beat a dungeon without killing any enemies besides the boss.
Beat Ickykolo on Savage with every class.
Beat Goaturku on Savage with every class.
Beat Big Tree on Savage with every class.
Beat the Bloated Grotto on Savage with every class.
Beat Hakkipunki on Savage with every class.
Beat Ignis Caverna on Savage with every class.
Beat Ensi on Savage with every class.
Beat the Floating Isles on Savage with every class.
Beat Uppmas Point on Savage with every class.
Beat the game on Savage with every class.