If Batman's (mostly) non-lethal methods of dispensing violent justice aren't doing it for you anymore, might I suggest the Red Hood? As you can see in this promo video for the Batman: Arkham Knight side-story, he's basically Batman with bullets for Batarangs.
This Red Hood is the assumed identity of Jason Todd, a former Robin who, after a few years of early retirement (read: being dead), was resurrected and went full-blown, criminal-killing vigilante. As you might expect, he and Bruce Wayne don't get along anymore, so he's not one of Batman's Dual Play team-up buddies - he has his own little campaign to play through.
For now, the only way you'll be able to play the Red Hood Story Pack is to pre-order Batman: Arkham Knight from GameStop in the US or GAME in the UK. Naturally, that means missing out on some of the other retailer-specific rewards, so you'd better check our list of Batman: Arkham Knight pre-order editions before you make any hasty decisions.