When it comes to Zack Snyder's DC cinematic universe, everybody kills. Superman did it in Man of Steel and Batman did it (more than a few times) in Batman v Superman: Dawn of Justice.
Perhaps it's not surprising then to learn that, in Snyder's grim DC universe, Batman's sidekick Robin also used lethal force.
Or at least that's the implication of the character using a deadly weapon like a halberd. The Boy Wonder's weapon of choice is revealed in Batman v Superman: Dawn of Justice Tech Manual from Titan Books, at which Digital Spy had the opportunity to take a peek. The book shows Robin's halberd in more detail, while also discussing how the broken version appeared in the film, at the request of Snyder.
We, of course, never get to see Robin wielding the weapon in action. Robin is killed by the Joker many years prior to the events of Batman v Superman, but we do get a glimpse at the sidekick's costume and broken weapon in the film in the Batcave, where it serves as a grim reminder of Batman's biggest failure. Most fans likely assumed the costume on display in the movie held Robin's signature quarterstaff. The character is frequently seen using the blunt weapon to battle bad guys in the comics and animated shows, so it made sense.
However, it turns out the broken axe head of the halberd seen in the movie simply made it look like a quarterstaff. Considering halberds were deadly weapons used frequently in medieval warfare, it's safe to assume Robin probably chopped off more than a few limbs during his time as the Boy Wonder. Too bad it couldn't save him from the Joker.
Not that Snyder would likely admit the implication of the character using such a violent weapon. He's taken plenty of flak already for Superman and Batman killing criminals, so it's likely he would rather not have even more fans angrily shouting to him about how Robin doesn't kill. Perhaps that is the reason behind the film not showing off the weapon's true nature — or maybe not. That would be giving Snyder too much credit.
