The Ending
Wow. On the one hand, a terrifically dark twist. (And how great that they had Reg E. Cathey's baritone to sell it, as we see that the ending has already become the stuff of local legend). On the other hand, it's a shame that the ending plays into the cultural belief that mentally ill people are inherently dangerous (as Horace noted last episode, Pete had never hurt anyone in his long life, and the show had up until this point done a great job of depicting the horrors of being in Pete's position).
Still, what a terrific run of episodes. Perhaps this is obvious to most, but it took me a few minutes of processing - Pete in his confused state presumably came back to the bar to kill Horace Senior, and mistook Horace Jr. for the dad (as foreshadowed by the excellent, chilling flashback showing CK as a terrifying Horace Senior).
The real tragedy is that, now that Pete is in the criminal system, he'll finally get at least some minimal level of treatment/medication that was unavailable to him on the outside. And presumably at some point he'll be lucid enough to have to live with what he did. What an absolutely horrifying, stunning ending. What a beautiful series.