Image: Bend Studio / PlayStationOfficial screenshot from Bend Studio / PlayStation.
One Percenter is the Platinum trophy for unlocking every other trophy in the base Days Gone list. Nothing in that list is missable, and one playthrough plus post-game free roam covers it.
Play the story, then clean up in free roam. The grindiest parts are the 989 Freaker ears, 541 looted items, 45 skills and three Allied camps. Track progress under Storylines, then Trophies.
Start looting human bodies from the first hour, since You've Got Red on You is the slowest counter. Kill Hordes after the story to finish skills, ears and trust together.