HellHound253

This achievement is unlocked by (obviously) completing all side quests. In your quest menu, given that you have a side quest active, it will appear under the "Side Quests" tab. If there is no active side quest, then the side quest tab will not appear. A checklist exists in game, which is accessed through the starting menu by clicking "Extras", then "Personal Statistics", and after scrolling almost all the way to the bottom, there is a section labeled "The Whole Story" checklist:" which will show you what side quests you have already completed, as well as which ones are not yet complete.