In the one-shot story we are introduced to Bruce Wayne of Earth -52.
Bruce is after Barry Allen a.k.a. the Flash. Bruce believing that the Flash is incompetent & that he should wield the Speed Force. Prior to their feud, Bruce asked Barry to help him save his deceased partners but Barry refutes the idea of going back in time due to his own regretful experience with time travel.
Batman and Flash battle it out, it seems that Flash has the upper hand by removing Batman from his vehicle. However, Barry was caught off guard, which gave Bruce enough time to inject him with the cryostasis formula. Despite Flash’s increased metabolism, he managed to knock him out within three seconds.
Barry wakes up and finds himself tied in front of the Batmobile. Bruce reveals that he repurposed the engine of the cosmic threadmill thus allowing him to harness Barry’s connection to the speed force. Barry pleads with Bruce to stop, telling him it will rip them both apart. But Bruce refuses to listen to him
Bruce's plan is successful in giving him access to the Speed Force, although one side effect is that he is now "fused” with Barry, or at least, he can hear his voice in his head.
Ultimately, Bruce realized his dreams as he’s now the most fearsome, but more importantly, fastest man alive.
Upon being recruited by The Batman Who Laughs, Red Death is sent to Central City, where he gains the attention of Iris West & Kid Flash. Red Death uses the Speed Force to age them to the point that they appear elderly. The Flash arrives & attempts to catch up to him, but Red Death uses his Speed Force bats to slow him down. He is about to finish Barry off, but Dr.Fate whisks him away. Red Death claims that they will battle again and wastes no time to make Central City reminiscent of the Gotham City of his Earth.
In Other Media
In the episode "Memorabilia", David Singh states that Cicada has killed more people than even the Red Death. Whether he appears in the series or not remains to be seen.