In what should honestly not be a surprise to anyone who saw Batman v Superman, it turns out that Batman's youthful sidekick Robin was also someone who preferred murdering criminals as opposed to sending them through that pesky justice system. As discovered by Digital Spy in their perusal of the Batman v Superman: Dawn of Justice Tech Manual book, the late Robin didn't wield his traditional quarterstaff when fighting bad guys. Instead he had a giant goddamn axe. Of course.
A halberd, to be precise: a two-handed battle-axe and spear which allows its users to both cut and pierce their enemies' flesh. (The blade and pointy bits are kept out of shot in the images above, but that's presumably it being held by the memorial of Robin's vandalised uniform.) The streets of Gotham City must have been littered with the severed limbs of many a criminal before the Joker finally stopped Robin's reign of terror.
Digital Spy also uncovered a few other, less murder-centric facts in the book, well worth checking out if you have a few minutes. Assuming Daily Planet editor-in-chief Perry White doesn't push you in front of oncoming traffic first.