Thomas Wayne, also known as Batman, is the superhero of the DC Comics.
Thomas became Batman when he and Martha Wayne witnessed their son Bruce Wayne get murdered by Joe Chill. Batman formed an alliance with Commissioner James Gordon, Judge Harvey Dent, and Oswald Cobblepot (head of security for the casinos used to finance Batman's war on crime) to deal with crime in Gotham City.
When Barry Allen entered the Batcave, Batman attacked Barry, but was surprised to hear Barry call him Bruce. Barry explained to the alternate Batman that Eobard Thawne altered the time line and gave him the details of Bruce's life after his counterpart's own death. Batman decided to help Barry regain his powers to change history in order to save Bruce.
After Batman's first attempt to restore Barry of his powers, he had to rescue Judge Dent's children from the Joker, who in this reality was Martha Wayne who went insane from her son's murder. Dent is distressed when the judge's twin children were kidnapped by the Joker, threatened Thomas Wayne with legal action unless his children are back. Gordon contacted Batman and tried to persaude that he doesn't need to fight crime alone. Gordon attempted to stop Joker on his own but ended up being trapped and killed. Batman couldn't kill Joker, and since he felt responsible for all her crimes. After Batman saves one of Dent's children who had accidentally been shot by Gordon during a rescue attempt, Batman resumed pursuing Joker. During a showdown, Batman revealed his recent discovery that they were supposed to die that night at Crime Alley and how they are alive now. Batman promised Joker he will bring their son back even if it costed them their lives which restored Martha. Martha fled from Batman when she learned Bruce would become just like him and fell to her death in the same hole Bruce fell into as a child.
After a second attempt successfully restores his ally's powers, Batman worked with the Flash to rally a team to oppose Eobard Thawne's changes to history. Batman, Flash, Cyborg, and Superman (after rescuing him from a government facility with help from Element Woman where he was held for experimentation) to deal with the war between Aquaman and Wonder Woman. Batman gave Flash a medicine to slow down the electrical activity in his brain since the speedster's memories were changing.
The heroes went to Themyscira to stop Aquaman and Wonder Woman. Batman stabbed Thawne in the back using an Amazonian sword and learned that altered timeline was actually created by Flash as part of an attempt to save his own mother. Before acting on this new information, Batman was fatally wounded by a traitorous Enchantress. Before Flash left to try and restore the old world, Batman thanked and gave Flash a letter to his son, expressing his confidence that Barry will recreate the better world Flash has spoken of and expressed his regret for what will happen to Barry's mother. The alternate Batman's letter encouraged Bruce Wayne to accept their deaths and move on, as well as encouraging Batman to pursue a closer relationship with Damian, and keeps the letter as a part of the Batcave's display dedicated to his parents' memory.