Comment Social skills abound! (Score 1) 655
He needs a guild or a bunch of "friends" behind him to accomplish a great many of these achievements. Even if he is in a huge guild that is defeating the most difficult end-game content, at some point there are going to be achievements that others are going to set out to do specifically and entirely for him (and maybe some others that luckily get to tag along)... The amount of achievements in this category is probably about 100-150 whereas the others are either able to be done solo or will just happen in any decent group.
So, he befriended his guild or his group of online friends, with or without their knowledge, to help him get to this end-goal.
We can even go further into specifics and say that the Quests completion may be more of an accomplishment than the Achievements completion. It is very easy to do about 3500-4000 of the quests in the game without any help, but beyond that there are chains that need help for sure. These hurdle quests don't make up the next 2000, probably only 100 or 200, but he still needs a group that he can call on whenever he hits that wall. Also remember those people may have already done the quest in some cases and are getting absolutely nothing out of it. In the case of achievements, at least there are a bunch of people (5-25) that are going to get that achievement credit if they haven't already.
Actually, I think this guy may have more social skills than most...