Ghost Recon: Advanced Warfighter - World Champion
When I found out that an Achievement like this even existed, I was shocked. In order to actually obtain the "World Champion" achievement, you'll need to be number 1 on the Universal Leaderboard in the game's Multiplayer. That's right, this achievement isn't messing around; either you're name is up on the top, or that's 40G you'll never see.
Quake 4- Number One
Thought the "World Champion" achievement was impossible? Well, Quake 4 has a surprise for you. In order to obtain the game's "Number One" achievement, you'll need to be ranked number 1 on the game's online leaderboard -- sounds familiar right? Well the difference here is that the leaderboard you need to be on top of is the All Gametypes one.
NBA LIVE 07 - Online With 1,000 People
This achievement is defiantly... different. It requires the player to be online when there are 1,000 other users on, or more on NBA LIVE 2007. The problem with this achievement was that even during the game's first months of release, having 1,000 people online at the same time was rare. On top of that, since February 2010, EA have shut down the game's server, making it impossible to obtain the achievement.
Guitar Hero III - The Inhuman Achievement
Yes, it really an inhuman achievement. In order for players to obtain this achievement, you'll need to complete "Through The Fire and Flames" on Expert difficulty -- for those of you who have Guitar Hero III, you know exactly how challenging this is.
If you actually have any of the above achievements, be sure to brag about it in the comments section & share your stories of hard achievements you've come across.