Game of Thrones' seventh season may go down as one with the fewest major deaths since Season 2. While we lost the sand snakes and Olenna Tyrell, these were always more minor characters in the Westeros pantheon. The only major demise came in the finale, when Littlefinger was executed, with Arya carrying out the sentence. Funnily enough, actor Aiden Gillen predicted Arya would kill Littlefinger two years ago, in the run up to Season 5.
Asking Game of Thrones actors how they will die is a pretty normal pastime in interviews, since everyone knows they could go at anytime. Some guess wildly, like Ramsay Bolton actor Iwan Rheon, who said he wanted to be killed by a dragon. Even those who guess more realistically rarely get their deaths right, proof that the show's twist and turns are hard to see coming, even when you're in the thick of it.
But Gillen guessed his death exactly right, ahead of the year where he married Sansa off to Ramsay. He said he figured Arya Stark, who at that point everyone knew would be entering the House of Black and White LLC and training to be an assassin, should be the one to kill him.
Even though he wasn't on her list, even though he'd barely made an impression on her in King's Landing, and only a small one in Season 2 at Harrenhal. He just sensed that Littlefinger being brought to justice would involve her using those skills she'd be acquiring that year to take him down.
Though Gillen didn't know it yet, he was reading his character's fate correctly. Littlefinger has been bound to the Starks from the beginning, taking down their family for never being allowed to marry Catelyn, while betraying Ned in hopes of getting her single once again.
Littlefinger's success in pulling the strings and causing the chaos that helped him climb was his ability to manipulate others into doing the deeds for him. He rarely let anyone see it was him as puppet-master. One of the few times he did was that moment with Ned from Season 1, "I told you not to trust me." It was a rare moment when his drive for revenge gave him the need to tell his victim who had done them in.
But while the Starks of the previous generation were Littlefinger's obsession, it was the Starks of the next generation that were his weakness. Littlefinger's feelings were too strong for Sansa, they made him act and then have to cover it up, which is not his regular modus operandi. He was therefore always weak around Sansa, as she knew the truth about Lysa's death.
As for Bran and Arya, Littlefinger simply didn't understand what they'd become. He thought them like Robb, or Ned, honorable to a fault, and shortsighted because of it. His complete failure with Bran at the beginning of this season was the first death knell we heard coming for him. His misreading of Arya (which the show insisted on playing to the hilt) was the second.
But Littlefinger's time was up either way this season. If there was a theme this year, it was that those who still played the game of thrones in the face of the Night King would not survive. Olenna's death was one -- she had no place in this new world. Cersei's abandonment by everyone when she refused to get on board, seeing the Night King as merely another piece on the board, was another. And Littlefinger's death was too. He was still playing the game, even this late in the day, trying to get Sansa to be another Cersei, to see that the ladder of chaos, and the climb for power, was all.
Turns out that ladder only goes so high, and when the rungs run out, it's a long way to fall. RIP Petyr Littlefinger Baelish. May you hit every rung on the way down.