Here is the full list of all 29 Heads Will Roll: Downfall achievements.
Achieve perfect relationship with Freya.
Get betrayed by Freya.
Kill an enemy with a crossbow shot to the neck.
Become a man-at-arms.
Become a sergeant.
Kill marauder boss.
Spare the Sheriff.
Kill the Sheriff.
Defeat De Monfort.
Achieve maximum Virtue.
Lower Virtue to zero.
Earn respect of the soldiers.
Torture the prisoner.
Refuse to take part in the torture.
Prove your worth to the sergeant.
Complete the game on any difficulty.
Pursue retreating enemies to the forest.
Pillage the Scottish camp.
Search for the Scottish army in the South.
Hide in the pond pretending to be a frog.
Use Flargum for self-punishment.
Refuse to work for the earl.
Find out what the smugglers were hiding.
Try to save yourself instead of Maria.
Try your best to save Maria... And still fail.
Defeat De Monfor using a wooden club.
Survive the encirclement.
Kill the Scottish spearmen.
Complete the game on maximum difficulty.