multiple versions of Colter's mind (spoilers) + critic about the end
At the end of the movie Colter replaces Sean. He is not technically stealing his life since Sean disappears in both scenarios : dead or replaced. So that's okay ethically speaking.
But in the new alternate reality where Colter replaces Sean, his mind exists in 2 distinct occurrences : in Sean's body and in his own comatose original body.
In this new reality Colter (comatose) is still waiting for his mission, and if it happens and Colter succeeds he might just do the same than with Sean and survive in another body in a new dimension that will then contain 3 occurrences of Colter's mind (Colter Sean, and his new vessel).
As long as there are missions for Colter in the successive new created realities there will be new versions of his mind if he "escapes" the same. And Goodwin just ends up arrested each time.
This is kinda weird.
About the end : I think the movie would have been way more beautiful and poetic if Colter's life ended on an infinite kiss in a time-freezed pocket universe.
(Unless of course if the Colter's mind multiple versions serve as a scenaristic device on an hypothetical sequel).