Here is the full list of all 30 The Legend of Korra achievements. It takes around 15-20 hours to unlock all of the achievements on Windows.
Spirit-bended 200 dark spirits.
Collected 10 cabbages.
Collected every treasure item.
Purchased 12 talismans.
Completed the highest difficulty of Pro-bending.
Completed the game on Extreme difficulty.
Maxed out all bending types.
Performed 100 Finishing Moves.
Won a Face-Off in a Pro-bending match.
Went into Avatar State 10 times.
Got 10 Knockouts in Pro-bending matches.
Obtained all combos.
Countered 100 times.
Completed Chapter 8.
Completed all tutorials.
Completed Chapter 7.
Dodged 100 times.
Used your first equipped item.
Equip your first item in Korra's Room.
Completed Chapter 6.
Bought your first item at the shop.
Completed Chapter 5.
Went into Clash Mode 10 times.
Completed Chapter 4.
Completed Chapter 3.
Jumped 100 times.
Entered the Collection Screen for the first time after finding a treasure.
Completed Chapter 2.
Completed a Naga Running sequence without hitting anything.
Completed Chapter 1.