Regicide Achievement in Dishonored
You assassinated the Lord Regent, Hiram Burrows
How to unlock Regicide
During Mission 6, your target is Lord Regent. You have a chance to kill him from afar a few times and even when he is in his room. If you are in high chaos, however, he will likely not stick around. He will flee to the roof where you must go to confront him. Kill him in any way to get the achievement.