Mike Hoffman said:
[...](I)t is Mako who dispatches his foe first, shocking Ming-Hua by using lightning on the water she is standing it. Of course, we have to ask why he didn't do that many episodes ago(.)
Yeah I found that fight pretty anti-climatic. He fights her of, but falls for her trap and they're on her turf now and then wham just pulls the Ace out of the Sleeve and it's over.
Thing is I don't think he could Lightning Bend until that moment, it was supposed to be his "Oh, I'm fucked" - Moment like Zaheer and Bolin had in the previous Episode (Unlocking Flight, and Lavabending).
And it's understandable, she was freakin' scary with her weird Waterlegs and the shadows she was casting.
Would've loved it if they'd have padded it out a bit and let them have they're fight with Makos new power.
But that's just my idea on why he suddenly pulled the lightning card, can't remember maybe he had used it before.