Here is the full list of all 29 Rogue Legacy achievements. It takes around 50-60 hours to unlock all of the achievements on Windows.
Use the special class at least once.
Put at least one point in every skill in the manor.
Find all the runes (purchase not necessary).
Beat the game... twice.
Defeat the trademarked chemical.
Beat one of the clown's games at least once.
Defeat the last boss.
Read the last journal entry.
Defeat the boss in the Land of Darkness.
Defeat the boss in the Maya.
Defeat the doppleganger.
Defeat the boss in the Forest Abkhazia.
Defeat all the minibosses.
Have one rune equipped in every item slot.
Reach level 50 or higher.
Have one piece of equipment in every item slot.
Defeat the boss in Castle Hamson.
Kill a chicken.
Die 20 times or more.
Choose a hero with no traits.
Earn your very first Enchantress rune.
Open your very first gold chest.
Find all blueprints (purchase not necessary).
Play the game for at least 20 hours.
Defeat the brothers.
Defeat the son.
Defeat the asteroids.
Mock the traitor.
WITHOUT using the Architect, complete the game dying 15 times or less