With her new boost in powers thanks to Cordelia's sacrifice, Mallory gains the strength to do the time travel spell and goes back to 2015, right after Michael grew 10 years overnight. Here we see a confrontation between Michael and his grandmother Constance after he kills a Priest. The fight results in Constance kicking Michael out of her house, feeling betrayed by the grandson she thought she was meant to love and raise until her dying day. Michael runs from the house and into the street where he's almost immediately hit by Mallory's car. Then promptly run over again, twice more. Just to really get the message across.
Since Mallory has gone back to a point where Michael is young enough not to be all powerful, he isn't able to snap back like he did after Madison shot him. Constance, who ran out after the commotion to find Michael dying in the street, cradles him in her arms. He asks her to take him into the Murder House so he can die there and be with her forever. Though she does give it a bit of thought, Constance tells her grandson to "Go to hell," and leaves him to die alone.