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