According to Eric Holmes, the creative director of Batman: Arkham Origins, the game was almost rated M with how brutal the combat is.
Arkham Origins has really intense combat action. We’re really pushing the edge of T for Teen with what we’re doing.I don’t think we could have pushed it further than we have without risking a rating bump.
The combat is described by the ESRB as having Batman “”punch, kick, and use fantastical weapons (e.g., electrically charged gloves) to defeat enemies.”
You’ll see for yourself once Arkham Origins launches later this month, on October 25th.
Source: Reddit via Gamespot.