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