The Tylered V'oq vs. Hippie V'oq fight should have gotten a deeper spin. The whole V'oq arc was left behind and not concluded in a satisfactory way.
I somehow liked the Disco Klingons, but the hate they got made them disappear from the show almost instantly. Q'rell was taken along, but the whole Klingon war was handled offscreen.
Under the Skin - with Scarlett Johansson. There's almost no dialogue. No exposition about anything, or names - just the short lifespan of an alien. Disguised as a woman, they're part of what seems to be a hidden alien colony living amongst humans.
The soundtrack is haunting, hypnotizing and beautiful.
It's also slow and sad.