Here is the full list of all 15 Time Splatter achievements.
Exit the Dungeon
Pick 30 Ammo Crates
Kill 50 Knights
Kill a Dinosaur
Kill 10 Knights
Kill 50 Plagued
Kill 50 Enemies
Kill 1 Knight
Pick 10 Ammo Crates
Kill 30 Enemies
Kill 30 Plagued
See the Game Over Screen for the First Time
Kill 10 Enemies
Pick an Ammo Crate
Kill 1 Plagued