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