Here is the full list of all 23 Undefeated achievements.
1,000 gold found
10,000 gold found
100,000 gold found
Kingly Lizard Slain
Sporarum Slain
Cracilia Slain
Giftly Shrine Visited
Mutant Raflesia Slain
Genu-Geko Slain
Spoiled Rocks Slain
Treesore Slain
Genesore Slain
Lurker Slain
Magasz Found
Beriberu Found
1 hour played
20 hours played
Finished in less than 6 hours
5 sidequests
All 16 sidequests
3 secret rooms
13 secret rooms
All 25 secret rooms