Nightwing
Nightwing is a fictional superhero appearing in American comic books published by DC Comics. The character has appeared in various incarnations, with the Nightwing identity most prominently being adopted by Dick Grayson when he moved on from his role as Batman's vigilante partner Robin.
Nightwing
When the Joker is told he is dying by his doctor, he unleashes Joker juice on the inmates at the Slab, causing a breakout. At the end of the arc, Nightwing is responsible for killing the Joker against the wishes of Batman and Oracle. Nightwing becomes depressed and Oracle tries to bring him out of it. Soon after, Batman manages to revive the Joker.