Xbox just unveiled Mythic Achievements, which are basically PlayStation platinum trophies
They signal to the world that someone has fully completed a game. And they apply retroactively to titles you've already finished.
Reports & sources
Polygon
Xbox’s Platinum Trophy Equivalent Officially Revealed (opens Polygon)Polygon's feed description
Engadget
Xbox just unveiled Mythic Achievements, which are basically PlayStation platinum trophies (opens Engadget)Engadget's feed description