Satsuki and the Four Devas up to the point where Satsuki stabbed Ragyou.
It was obvious from the start they were sisters, but that reveal unleashed a minor shitstorm on her character.
There was a couple nice bits like Gamagoori being based and Satsuki's onee-san power scene but there's no deny the finale wasn't at the same level as the rest of the series. It was too generic for it's own good and felt very rushed. It did a poor job making noticeable the collaboration of any character not named Ryuuko and Senketsu. We got she's the hero but one of the series strengths is in the characterization which apparently they put aside at the end.
"It was okay." -IGN
Other animes are you even trying?