Jason Todd's resurrection scene and his sequential freak-out. After they drop him into the Lazurus Pit, he bursts out of the water screaming like a madman, with a crazed look in his eyes. He kicks the crap out of Ra's Al Ghul's men, taking out one by jamming his thumbs right into the poor sucker's eye sockets. He then escapes by jumping out the window. His actions from this entire scene are borderline... animalistic. Though resurrection via a Lazarus Pit renders the one resurrected momentarily insane, even Ra's Al Ghul was afraid. What makes it more terrifying is Vincent Martella's performance. Just imagine Phineas Flynn screaming like he's in horrible agony.
One of the kills the Red Hood does: he stabs a criminal in the eye with a tazer and then turns it on full-force, short-circuiting his cybernetic eyes and blowing up his brain. While in the movie, it's done to one of the Canon Foreigner group, the Fearsome Hand of Four; in the comic, it's done to Captain Marvel baddie Captain Nazi.