In Bioshock Infinite, the last boss is you. You find out that you're the guy you've been fighting the whole time - from a different reality.
As the story goes, Booker DeWitt went and got baptized after the battle at Wounded Knee and became Comstock. As the prophet, he became somewhat sterile, so he enlisted the twins, who had figured out how to transverse realities, into opening a hole into the one where he didn't get baptized but ended up a gambler. That's the one where he had a daughter, and he kidnapped her.
That's right. Elizabeth is his daughter that he kidnapped as Comstock, and the only way to stop Comstock is to go back to the baptism and die.
Kind of a bunk ending after all that you go through to get there - Elizabeth actually has to kill you. That's the way it ends.