Split (2016): written and directed by M. Night Shyamalan; starring James McAvoy (Kevin Wendell Crumb), Anya Taylor-Joy (Casey Cooke), and Betty Buckley (Dr. Fletcher): AKA, the movie spoiled by its own sequel. Oh, well. To stay spoiler-free, note that Split is something of a return to form for M. Night Shyamalan when it comes to weird suspense involving psychiatrists and psychiatry.
James McAvoy plays a man with a lot of multiple personalities (or 'Alters'), some of them evil, some of them good, and some of them ambiguous. He kidnaps three teen-aged girls because he's going to do Something Awful to them. So begins a battle of wits between the teens and Multiple McAvoy, primarily between him/her/them and Anya Taylor-Joy's depressed outsider with her own horrible secret in her past.
M. Night Shyamalan does a fairly solid job of not getting too mired down in the sadism that usually accompanies such closet dramas, and McAvoy really is very good as most of his personalities (though he hams it up with a broad Brooklyn accent). Taylor-Joy is excellent in a role somewhat similar to her star-making turn in The Witch -- as an outsider discovering her own power when faced by dire circumstances. Recommended.
Pi (1998): written by Darren Aronofsky, Sean Gullette, and Eric Watson; directed by Darren Aronofsky; starring Sean Gullette (Max Cohen), Mark Margolis (Sol Robeson), Ben Shenkman (Lenny Meyer), Pamela Hart (Marcy Dawson), and Samia Shoaib (Devi):
Darren Aronofsky's first feature should probably list David Lynch's Eraserhead as an inspiration in the credits, most noticeably in a stylistic sense. Its thematic concerns are different, however -- Pi is a puzzle story about stumbling upon answers to questions that probably should not be asked.
Lead actor Sean Gullette is not the most charismatic actor in the world, which is something of a problem when doing a movie with so few even mildly sympathetic characters (see also Aronofsky's next film, Requiem for a Dream, which is what would happen if Trainspotting were run through a humour-and-sympathy scrubber). It's an enjoyable debut, but certainly not deep in any way unless you've never heard of the Kabbalah. Recommended.
Slenderman (2018): written by David Birke based on a character created by Victor Surge; directed by Sylvain White; starring Joey King (Wren), Julia Goldani Telles (Hallie), Jaz Sinclair (Chloe), Annalise Basso (Katie), Alex Fitzalan (Tom), and Taylor Richardson (Lizzie): Massachusetts is the setting for this terrible horror movie based on an Internet meme/ fake urban legend. It's no more terrible than a lot of recent horror movies. And it does have an almost all-female cast.
A much scarier tale is the HBO documentary Beware the Slenderman, in which all the horrors are human.
However, as the female characters are denied all agency in their struggle with the Slenderman, the whole thing ends up being another nihilistic mess. Slenderman himself is sort of what you'd expect if a committee work-shopped the creation of a mythical creature -- he's a tall, faceless guy in a suit.... with tentacles that sprout out of his back! And a magical house somewhere in the woods! And three bells announce his arrival! Ouch. Not recommended.