Level 88 Attained - Lineage I
This one goes back quite a few years but shows just how much easier MMO's have become in terms of leveling. Lineage was an old-school MMO that's leveling curve would be considered 'trollish' by today's standards. As you reach higher levels, the amount of experience you earn is fractioned. At level 80, experience gain is 1/64 of what it was at level 60.
The game was released in 1998 and it seems only one player has ever managed to reach the level cap of 90 during this time, and that recently happened in February of this year! It took him three years to reach it. Can you imagine the outcry if it took three years to reach level 90 in any MMO that's popular today?