SPOILERS AHEAD for American Horror Story: Apocalypse Episode 10: "Apocalypse Then"...
We are nearing the apocalypse (again). Cordelia and Myrtle are with the girls, going over all the stuff we already know: that Coco and Mallory will be under an identity spell so Michael can't sense them; that Mallory's powers will surface when the time is right, etc. There is a bunch of really sappy "I love you" moments, then the spell is cast.
We next see Coco and Mallory being taken to the salon. Madison is their Uber driver. On the drive, Madison sees a poster for Dinah's new talk show, and she storms back to Cordelia and Myrtle to report on this. She wants to burn Dinah for making a deal with the devil, but Cordelia insists they can use her after the apocalypse, and she worries that killing her would reveal their plan.
Cut to post-apocalypse. Cordelia, Myrtle, and Madison rise from the dirt like zombies and march into the outpost. They wake the witches, and Dinah wants nothing to do with whatever they are planning. Michael offers them a deal: they pledge their fealty to him, and he won't kill them. Cordelia laughs at this, but Dinah is all in. She chooses the winning side. But then Marie Laveau strolls in. Cordelia made a deal with Papa Legba, trading Marie for Dinah. Marie kills Dinah. Mead pulls out her gun-hand, Cordelia whispers a chant, and Mead explodes. Madison grabs the gun and fills Michael with bullets. It drops him, but it is clearly only temporary. Myrtle grabs a lock of his hair and gives it to Mallory so she can use it for her time travel magic.
The witches rush upstairs, and run right into Brock - who I forgot all about. He stabs Mallory, so Myrtle sets him on fire and they take Mallory to a bath, trying to heal her. She isn't strong enough, so Cordelia knows what she has to do. She faces off against Michael, who is ready to kill her. But Cordelia uses her magic to take the knife from him and stabs herself. Her death gives Mallory the magic that she needs to fall into her time-travel spell. She goes to 2015, where, when Constance kicked Michael out of her home, Mallory was driving a car that hits Michael. She runs over him three times, then drives off. Constance watches him die, and refuses to let him die on the property.
So, everything is back as it was. Mallory still remembers everything that happened. She joins the coven. Zoe and Queenie are still alive. Myrtle and Madison are still dead. But Nan, still a disciple of Papa Legba's, brings Misty back - some sort of thank you from the evil for taking care of the son of the devil. The apocalypse doesn't happen, and everyone lives happily ever after.
But evil never dies
As a sort of post-script, Emily and Timothy still meet (another pair of characters I forgot about) in the year 2020. They have a baby a year later, and three years after that, they come home and discover their toddler killed his babysitter. Anton LaVey and his minions show up to "help" with the baby. So clearly, nothing can be done to prevent the antichrist from rising. He always finds a way. That is better than the "happily ever after" ending the show appeared to have... but not a lot.
I did not like that ending
Call me a cynic, but I was hoping that everyone would die, the apocalypse would stand, and... well, I don't really know what Michael was hoping to get out of that. But that is the ending I was hoping for.
Apparently, as a kid, Michael didn't have his power
Why would Michael be able to die by being hit by a car? A machine gun couldn't keep him down, and it's not like he gained his powers as an adult - he had just finished aging ten years in the span of an evening. That just feels like sloppy storytelling.
There was a lot of death
In addition to Michael's death, Cordelia made Mead explode. Marie took a machete to Dinah's head. Michael snapped his fingers and caused Madison's head to explode. He also ripped Marie's heart out of her chest - and took a bite for good measure.
So... the time travel thing
After Mallory killed Michael in 2015, did she return to the "present"? But that no longer existed. And if she stayed in 2015, she would overlap with the 2015 version of herself. But it had to be the "now" Mallory who stayed in 2015, because she remembered everything that happened. Ugh, I hate time travel.