This achievement can't be missed and will come from natural story progression.
To be honest there is no necessity for a guide on how to get this achievement. Since you cannot fail it. However there seem to be quite a few problems with the achievement unlocking system of this game and the Xbox one in general. So I thought it could be useful to have a little reminder when this achievement should unlock so you know that nothing glitched for you.
I will mention the actions you have to participate in right before you get your achievement below.
*** Spoiler - click to reveal *** After you gain control of Lord Ethan for the second time you have to punish a thief in your castle's courtyard. You must decide what kind of punishment you see fit. Personally I chose to let him go unpunished. And I unlocked this achievement right after this decision.
Just in case you need further information about the situation described above you can refer to the video below (video credit goes to: GamerPerfection)
Hope this helps you guys ;-)
Any improvements? Let me know in the comments!