The Steam achievement in Darkchaser is quite interesting—one of them requires you to travel the distance equivalent to circling the Earth once, and another requires the distance from the Earth to the Moon. However, I still want to complain: is anyone actually able to complete this? I know it's a game that requires you to run around all the time, and I've already played for 100 hours, but it's still far from enough :D
Not every achievement is meant to be attainable (by everyone)
Unattainable achievements aren't achievments, they are lies.
Some might be extremely difficult or tedious though.
I should qualify it as unattainable for most, though these two are just grindfests.