Who is the fastest man on earth?

Bart later reappeared, several years older, in Tokyo wearing his grandfather's costume. He later helped the heroes against the army of escaped supervillains in the Battle of Metropolis. Bart then explained to the nearby Wonder Girl that his grandfather's uniform was the only thing that could survive the trip back from where he had been, and that he was the only one there "who could still run". Bart then unleashed his anger against Superboy-Prime for killing Conner Kent, pummeling him at super-speed and forcing Superboy to retreat from the battle. When the crisis was over, Bart explained to Jay that he spent years in an unknown dimension where he grew older. Bart confirmed that the Speed Force was destroyed and that he used up the residual speed locked in his body fighting in Metropolis. He gave Barry's costume to Jay and said that Jay was once again the fastest man alive.