The Chosen Ones

Aren't you going to show the achievements on the multiboard so people can judge their progress anyway? And will you need to do all the achievements in one playthrough because they reset from prologue? That's pretty bad, because the game is so based around give-ups and playing multiple times.

Achievements should be challenging and interesting. Dodging an attack by going invisible is interesting and challenging. Missing 20 steals is funny but boring as heck and is a massive grind.

Flecky's suggestions are more interesting and unusual, some of them at least. Admittedly some are pretty ridiculous.

Aero's are pretty boring and really standard, it's not really challenging or fun to obtain 999,999 gold.

Depends what sort of system you want really.