OP summon one shots him. Wasn't expecting that. And she still had a bunch more contingencies! Guess he and his clone were right about how the fight was going to go in their earlier conversation. Still, hell of an ending. Good show!
Imagine how much of a mindfuck it would've been if instead of telling the story this way, they showed us nothing of her perspective, and told us nothing of the 17th floor, and when the MC showed up to clear it the first time, it showed us this fight entirely from the copy's perspective? Then after she won they could've retroactively showed us the buildup and explanation.