In DC lore, Barry Allen or Wally West. Now, as a new era of speed begins in the The Flash #1, there can be no more debate.
The synopsis for the The Flash #1 from Simon Spurrier and Mike Deodato Jr. promises that Wally has "never been quicker, more fulfilled, more heroic," and reveals that he will be experimenting with "his evolving understanding of his powers." Recently, Wally West unlocked the ability to run through different dimensions. This differs from Barry and Wally's shared ability to vibrate between realities, as these aren't alternate worlds in the multiverse, but different 'levels' of reality, full of new and unexpected mysteries and their own physics. With this upgrade, Wally isn't just technically faster than Barry - he explicitly has an extreme power his mentor doesn't.
Wally West Sures Barry Allen with New Flash Power
Originally the sidekick Kid Flash, Wally West is officially the fastest version of Flash, having sured his former mentor Barry Allen multiple times over. However, he took a long road to doing so. After Barry's death in Crisis on Infinite Earths, DC took the opportunity of the shifting mantle to decrease the new Flash's speed, making the hero less over-powered in its new canon. Originally, Wally could run slightly faster than the speed of sound, while Barry could run at the speed of light. Over the years, Wally caught up to his mentor's top speed and eventually sured him... only to be kicked out of reality. In DC's New 52 reboot, Wally was controversially retconned out of existence, with Barry Allen back front and center as the Flash. While this decision was later reversed, Wally was once again relegated to being Barry's second-stringer, and only recently reclaimed his rightful place as DC's main Flash.
Wally West's Flash Is Officially the Fastest Man Alive
Because of this rocky road, many fans have viewed Wally's 'Fastest Man Alive' status as either temporary or without substance. Sure he's faster than Barry now, but what does 'faster' really mean for two people who are already moving at light speed? How long until Barry learns a new trick to go even faster? Even recent Flash stories have frequently seen one of the speedsters somehow increasing their top speed in a way that doesn't feel meaningful - extending a boundary that already felt infinite. However, Wally's dimension-hopping bucks this trend by not just making him faster, but allowing his speed to do something that's unique in DC lore.
Wally has unlocked dimensional travel while Barry hasn't, and even has the ability to move "beyond the Speed Force." Introduced in Flash #800's 'Between Love and You' - from Spurrier and Deodato Jr - Wally unlocked his new ability after coming into with an extradimensional mirror. DC's marketing materials have made it clear that this adventure unlocked Wally's dimension-hopping potential, and that his experience has "attuned his senses to strange new ideas." If you need a Flash who's fast enough to traverse levels of reality, Wally is the only choice.
Wally West Is Running Beyond the Speed Force
DC has spent a lot of time reassuring fans that Wally West will remain the fastest Flash, but now that argument is finally convincing, as his speed allows him to do things Barry Allen can't. As a classic hero, DC has little taste for limiting Barry's abilities, but by opening a new horizon for Wally's speed, it doesn't have to. The fastest Flash can not only run at impossible speeds, vibrate through solid matter, and travel between realities (just like the second-fastest Flash), but can now access hidden dimensions with new speed-based senses. After years of unconvincingly arguing for Wally West's superior speed, DC has finally given the current Flash powers that his mentor Barry Allen never had, actually presenting a convincing case for why fans should buy that he is - and will continue to be - the one and only Fastest Man Alive.
The Flash #1 is coming from DC Comics September 26.