“Rational!Harry has already taken the Unbreakable Vow. Rational!Voldemort, especially if he doesn't have his horcrux, and knowing that there's no negotiated way to escape the confrontation, will set up a deadman switch that destroys the world in the event of his own death, and tell Rational!Harry so in Parseltongue. I won't call it checkmate, but Rational!Harry cannot do things past this point that run the *risk* of destroying the world, which is a pretty severe condition. He has to be cert...
