The rarest Xbox achievement is the '1,000,000 Gamerscore achievement'. This achievement requires a player to accumulate one million gamerscore points across their entire Xbox profile. This is an incredibly difficult challenge, as it requires players to reach the maximum score in every available game on the Xbox platform. This means that players must complete every single quest, mission, and challenge within the game and obtain every single achievement associated with it.
In order to complete the 1,000,000 Gamerscore achievement, players must also complete any post-game content, such as downloadable content and expansions, as well as any other additional content. The total amount of gamerscore points needed to complete this achievement is around 1,000,000.
The 1,000,000 Gamerscore achievement requires a lot of dedication, as well as a lot of time and effort. Not only does the player have to complete all of the content within the game, but they also have to go back and complete any post-game content that may be available. This can take months, and sometimes even years, to complete.
The 1,000,000 Gamerscore achievement is also incredibly rare. Very few players have been able to achieve this feat, and it is likely that only a few will ever be able to do so. It is an incredible accomplishment, and those who have completed it are revered in the gaming community.
So, if you are looking for the rarest Xbox achievement, then the 1,000,000 Gamerscore achievement is the one to aim for. It is an incredibly difficult challenge, but one that is incredibly rewarding for those who can complete it. With dedication, hard work, and a lot of time, you too can join the select few who have achieved the 1,000,000 Gamerscore achievement.