Here is the full list of all 28 Loop Odyssey achievements.
Break both scarecrows in a single loop
Escape the loop
Slay the king
Get the girl
Kill everyone and break the loop
Finish the game without murdering innocent people
Finish the game with a loop under 100 second
Finish the game with at least 100 gold
Pet the dog
Find all elves
Finish the game with at least 350 gold
Talk 7 times to each citizen in town in a single loop
Reach crossing level 200 on a square of the map
Interact with the bench
Kill the Chancellor before the Assassin
Get your heart level over 100
Get your body level over 100
Get your spirit level over 100
Reach 5000 total loops
Reach 10000 total loops
Use a lookout tower 13 times in one loop
Kill the necromancer after dating her
Upgrade the club 10 times in a single loop
Talk to the Caporal with 4 hats in your inventory
Die by the Chancellor's hand with the amulet in your inventory
Talk to the Firefly Queen with the slug in your inventory, without having killed or interacted with any Fireflies/Firebats
Kill a guard with your bare hands
Kill the demon with the club and wooden shield