Amon was a great villain until that episode too. His defeat was poorly done and so anticlimactic. Korra suddenly knowing air bending after she lost her bending was just a head scratcher. By the time Buumi shows up, there's not really anything for him to do because the conflict is implied to already be over. Korra is established to have poor spiritual connections yet suddenly can use the Avatar state with ease. There's no growth left for her because she can do all the bending and the Avatar state. Again, makes it feel this was originally the end of this series.

What should have happened is instead of using air bending to fight Amon, she should have entered the Avatar state to save Mako. Her connection to her previous lives in that state could have given back her bending abilities, and she uses that to fight Amon and defeat him. However, I'd make it that this fight doesn't happen until Buumi has arrived and an all out fight is going down between the benders and Amon's forces. Then, when Amon gets defeated and exposed, it's in front of all his followers and fighters. They all surrender, and seeing his plan is ruined and he can't hope to salvage it, goes on to face the demise he originally has.

Korra meanwhile is shown to have the ability to bend, but it's very weak. She has to improve her spiritual connections to get strong again, building off the idea she is bad with that and that the Avatar state is proof that the spirits can help her get back to normal. That way even though there's no current conflict, we at least have an idea what Korra is going to do moving forward and it makes sense with what was established already.