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