The Elder Scrolls Online, Zenimax Online's enduring MMO based on, well, you know what it is, has dethroned Halo: The Master Chief Collection in one very specific category: it's now the Xbox game with the highest obtainable Gamerscore.
Per True Achievements, Halo: MCC has been the game whose achievements equate to the highest possible Gamerscore for many years now, but with ESO's new Feast of Shadows DLC, which just launched on consoles after a couple of weeks on PC only, the MMO is the new Gamerscore king - but not by much.
