Here is the full list of all 8 Flight of the Paladin achievements.
Complete the Campaign Stage "Ruins of the Count"
Survive 60 seconds in Survival Mode
Hear all music in Survival Mode
Obtain a score of 10,000 Points in Survival Mode
Defeat all three bosses in Survival Mode in one playthrough
Defeat 100 Monsters in Campaign Mode.
Complete the Campaign Stage "The Hollow Road"
Complete the Campaign Stage "The Woods"