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