Batman #614 by Jeph Loeb

In the aftermath of a close friend’s apparent murder during a chaotic opera heist, the city’s vigilante loses control and brutally assaults the Joker, teetering on the edge of breaking his moral code. Commissioner Gordon confronts him and demands restraint, while Catwoman tries to pull him back from the brink. As grief gives way to grim resolve, hints emerge that the tragedy is part of a larger plot manipulating events from the shadows.