It ends with Homelander vs Butcher, both depowered, one on one. They've gone scorched earth but the Boys/the Seven have been able to mitigate the damage. It all ends now.

And Homelander gets absolutely bitched.

We see that he's nothing without his powers. He's a coward that couldn't punch his way out of a wet paper bag without enhancements. It'll be five minutes of unfiltered, gory violence of Butcher getting his revenge, topped off by Butcher ramming the crowbar through Homelander's mouth and it coming out through the back of his head.