Superman enters the Batman - Zur-En-Arrh - Failsafe showdown in Batman #127

gamesradar.com:

Clark Kent may not agree with Bruce Wayne's tactics for keeping tabs on his colleagues' weaknesses, but at the end of the day, Justice Leaguer Superman will always help his teammate, Batman.

And never has that been more apparent than in Batman #127, written by Chip Zdarsky, illustrated by Jorge Jimenez, colored by Tomeu Morey, and lettered by Clayton Cowles.

Batman #127 reveals that Batman's psychological backup for if his personality is ever altered against his will, Batman of Zur-En-Arrh, has taken Bruce's place in the fight against Failsafe. 

As Zur-En-Arrh explains to Tim Drake, he created Failsafe as a backup in case Batman ever needed to be completely destroyed – something Bruce Wayne could never do.

This information is presented after a flashback in which we see Clark and Bruce argue about whether it was ethical for Bruce to keep files on how to destroy the Justice League, should such a thing ever be necessary. 

In the flashback, Superman asks what the JLA is supposed to do if Batman ever goes rogue, and Bruce admits he also has a contingency plan for that – but as Clark points out, such a thing won't really work if Bruce knows how to beat his teammates right back.

What Clark doesn't account for is that Bruce's backups have backups, as illustrated by Zur-En-Arrh creating the uber-strong, uber-fast, uber-technical Failsafe, a robotic force that nearly wiped out the entire Bat-family in Batman #126.

Despite Clark's anger, however, when Failsafe is just about to crush Batman – not Bruce Wayne, but the "pure" Batman of Zur-En-Arrh – Superman arrives in the knick of time to save the day. And Failsafe may be equipped to defeat Batman, but it's unclear if he's strong enough to beat the Man of Steel.

For Bruce's part,