A new series recently began known as the Dark Nights: Metal event, in which DC Comics plans on telling stories that exist within a Dark Multiverse that co-exists alongside the mainline DC Universe. In this Dark Multiverse exists several evil versions of the Dark Knight himself,
and one of them goes by the name of Red Death, who's an amalgamation of Batman and the Flash.
In the story, Batman: The Red Death, Bruce is seen aged and alone, having lost all of the Robins. He decides to go back in time and change things for the better (like that ever works). And so, he hunts down Barry Allen and effectively steals Barry's superspeed by attaching him to the Batmobile and driving it directly into the Speed Force, merging Barry and himself into the Red Death.