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.
Collected 10 cabbages.
Went into Avatar State 10 times.
Purchased 12 talismans.
Obtained all combos.
Won a Face-Off in a Pro-bending match.
Got 10 Knockouts in Pro-bending matches.
Spirit-bended 200 dark spirits.
Maxed out all bending types.
Performed 100 Finishing Moves.
Completed a Naga Running sequence without hitting anything.
Completed Chapter 8.
Completed all tutorials.
Completed Chapter 7.
Completed Chapter 6.
Completed Chapter 5.
Countered 100 times.
Completed Chapter 4.
Dodged 100 times.
Went into Clash Mode 10 times.
Completed Chapter 3.
Jumped 100 times.
Used your first equipped item.
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 Chapter 1.