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