House Baelish (or: GUHUUHGHHHGHGHH)
Not a great way to go out. Littlefinger’s plot and/or what little hold he had over Sansa couldn’t withstand two power player siblings. It’s a bit unclear just when Littlefinger was foiled, but if we default to Occam's Razor, we’re supposed to believe that he brought about his own end by planting the idea of him being bad in Sansa’s mind. First, there was this Season’s "fight all battles at all times in your mind" advice, and this episode there was an "always assume someone has the worst intentions" advice. This is playing it loud enough for the cheap seats as far as "causing your own downfall" is concerned.
Just like the show yadda-yadda-yadda’d over Sansa actually figuring out Littlefinger’s scheming, which leads her to question Bran about all Littlefinger’s doings, the show yadda-yadda-yadda’d over the part where we understood what Littlefinger was up to. He was Lord Protector of the Vale and Sansa was going to keep him around. Pressing his luck to stir the pot amongst the Stark siblings makes no sense. Even if his conversation with Bran freaked him out, if he loved Sansa, wouldn’t he be working to ensure Bran’s exposition bomb doesn't go off, not toy with Arya to gain total domination?