Two Alliance players, a human priest from Russia and a night elf druid from the US, have already unlocked every achievement currently in World of Warcraft, all 2511 of them. A lot of them are incredibly hard to get, but unlocking all is pretty amazing. And, according to Wowprogress, a few others are close to catching up with only one or two achievements missing.
Reaching 20,000 points is pretty incredible on its own, but going beyond 2500 achievements, or 25,000 points sounds insane. It means they had to collect 300 mounts, which will be quite difficult even after Legion comes out, more than 250 toys, all the pets and so on. They also had to unlock all the crazy PvP (killing 500 Pandaren players in Ashran, anyone?) and Arena achievements, all the Challenge modes and Mythic raids. It's no surprise that, according to their Armory stats, the last ones they sniped were mostly PvP and Season 3 related. Those are just painful, due to various weekly caps and time limits.
As you can see in the pic above, one of the achievements — "Mythic Dungeoneer", which can't be unlocked right now — is bugged in the Dungeons & Raids tab, but otherwise everything checks out. Legacy achievements, that are no longer obtainable due to gameplay changes, push the list beyond the 100% limit. Some achievements are worth 5 points, some worth 10, 20, 25 and so on.
This, and playing the game non-stop, is how reaching a whopping 25,825 points is possible for Alliance players and 25,815 for Horde. The 10 point difference comes from an Ashran achievement (Down Goes Van Rook) that has no Horde counterpart and therefore can't be completed by them.
Incredible stuff, and although there's no list of achievements for Legion yet, we might see players with more than 30,000 points soon.