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 every treasure item.
Went into Avatar State 10 times.
Collected 10 cabbages.
Completed all tutorials.
Completed the game on Extreme difficulty.
Purchased 12 talismans.
Completed the highest difficulty of Pro-bending.
Obtained all combos.
Maxed out all bending types.
Performed 100 Finishing Moves.
Got 10 Knockouts in Pro-bending matches.
Countered 100 times.
Went into Clash Mode 10 times.
Completed a Naga Running sequence without hitting anything.
Won a Face-Off in a Pro-bending match.
Completed Chapter 8.
Completed Chapter 7.
Completed Chapter 6.
Completed Chapter 5.
Completed Chapter 4.
Dodged 100 times.
Used your first equipped item.
Completed Chapter 3.
Jumped 100 times.
Equip your first item in Korra's Room.
Entered the Collection Screen for the first time after finding a treasure.
Bought your first item at the shop.
Completed Chapter 2.
Completed Chapter 1.