The Batman Who Laughs (Possible Season 3 Outcome)
For those who haven't been keeping up with the comics, "The Batman Who Laughs" is a corrupted hybrid of Batman and The Joker from an alternate reality. But in Telltale's continuity, he could be something else.
If Telltale's Batman trilogy climaxes with some kind of final confrontation between Bruce and John, one possible (determinant) ending could have Bruce kill John. This is basically what happens in the comics, but the context of the killing could be different depending on our relationship with the Joker by this point. If Bruce and John are enemies, the scenario could unfold much like the one seen in the comic book:
This results in the Joker expelling a gas from his mouth that rewrites Batman's brain ti give him a more sociopathic personality, thus creating The Batman Who Laughs. The Joker essentially turns Batman into another version of himself as a final act of ultimate revenge.
However, if we're friends with Joker (or at least former friends), John's motivations could be slightly different: He'd see Bruce as the only one capable of assuming his mantle once he's gone. Bruce doesn't necessarily have to inhale any kind of gas to become The Laughing Batman; he'd just have to go insane on his own. Telltale could then attach an epilogue where we briefly control The Batman Who Laughs, but this time, our decisions would have to be far more limited, as we're basically in control of a lunatic. (Hence why it would only happen in an epilogue.)
However, unlike The Batman Who Laughs seen in the comics, OUR version could be a little more...selective with his prey. He wouldn't go completely off the rails by destroying the entire planet, but he'd unleash hell on his rogue gallery in a way we've never seen before. Alternatively, he could transform all of Gotham into a haven for the mad and the deranged, thus providing a more lasting solution to the new breed of super-criminal that has emerged following Batman's first appearance in Gotham by providing an entire city for them to play in to their hearts' content.
Just an idea.