Back in 2018, a World of Warcraft player by the (in-game) name of Xirev made a splash when his Blood Elf Mage managed to, well, beat the game. That means earning all 3,314 achievements in the game, completely filling all of those bars, which also required filling a very large number of other bars along the way. It was a lot of work. It took him about 900 days of play time. It was significant. And now he’s done it again with Battle for Azeroth, clocking in a clear on all 3,927 achievements now.
Interestingly enough, this doesn’t quite mean he has everything in the game; at this point he has 484 of the 555 mounts available, which means that there are still things for him to pursue even after he has literally achieved everything the game chooses to track. But, you know, he’s earned a bit of a break until Shadowlands if he wants one. Also, the ultimate rejoinder to anyone asking him to link achievements.