If Batman Killed Joker

Over the years, Joker has tainted Batman with self-compromise and deception by paralyzing Barbara Gordon and killing Jason Todd, but if Batman fully succumbed to killing Joker and breaking his moral code of not killing, then he would never come back as Batman again.

Characters

 * Bruce Wayne/Batman (Dennis Quaid) - crosses a line when he killed Joker, and gives up his crime-fighting career and role of Gotham's protector
 * Joker (Martin Short) - he paralyzed Barbara Gordon in The Killing Joke and beat up Jason Todd with a crowbar in A Death in the Family, causing Batman to finally snap at Joker when he killed Jason Todd, in their final battle, Batman chokes Joker to death
 * Alfred Pennyworth (Ian McKellen)
 * Commissioner Gordon (Gary Oldman)
 * Barbara Gordon (Sarah Michelle Gellar) - paralyzed by Joker to drive Gordon insane
 * Jason Todd (Jenson Ackles) - got blown up and left for dead by Joker to torment Batman
 * Dick Grayson/Nightwing (Stephen Amell) - assumes the role of Batman.
 * Harley Quinn (Pauley Perrette) - after Joker's death, she returns to be a psychiatrist
 * Vicki Vale (Evangeline Tilly)
 * Lucius Fox (Morgan Freeman)
 * Selina Kyle/Catwoman (Angelina Jolie)
 * Leslie Thompkins (Glen Close)
 * Harvey Bullock (Vincent D. Onofrio)
 * Thomas and Martha Wayne (Kevin Conroy and Tara Strong) - Flashbacks
 * Joe Chill (Paul Backthorne) - Flashbacks
 * Penguin (Alfred Molina)
 * Two-Face (Tommy Lee Jones)
 * Riddler (Matthew Gray Gubbler)
 * Scarecrow (Charlie Adler) - follows Joker's legacy
 * Killer Croc (Kevin Micheal Richardson) - follows Joker's legacy
 * Poison Ivy (Iggy Azalea) - a scientist under Scarecrows employment.
 * Mr. Freeze (Hugo Weaving)
 * Bane (Cheech Marin)
 * Clayface (Gary Anthony Williams)

Plot
Batman and Nightwing attack Joker at his criminal headquarters, we discover that Batman is angry at Joker for killing Jason Todd, but Joker laughs as it is fun to break Batman in certain ways, Nightwing cuffs Harley, while Batman confronts Joker in a fist fight, while wearing brass knuckles to punch Joker numerous times and shouts "This is for paralyzing Barbara Gordon!", "This is for stripping Gordon and torturing him to see naked pictures of his daughter!", "And this is for beating Jason Todd to a bloody pulp and letting him die in an explosion!", Joker laughs at hearing Jason Todd and not Robin, "Oh, you're not mad at me for killing Robin? I'm sorry I killed Jason Todd....Bruce, thanks for the hints, Batsy, I knew it all along, adopting Dick Grayson after that Haly's Circus tragedy, bringing in the Commissioner's daughter in a fight with Killer Moth, then all of a sudden you adopt Jason Todd going against Two-Face, is it true Kathy Kane was Batwoman, what's next, Brucie?, are you going to what you want after I killed-?", Batman interrupts him by grasping his hand around Joker's neck, choking him, "Go on, cry for your dead mommy and daddy, see if they'd be proud of your-", but Batman uses the other hand to grab his neck, while Joker laughs as Batman tightens his grip on his arch-enemy's neck, then suddenly Joker's laugh turns into a cough of near death, despite Nightwing's protests to stop his mentor from killing Joker, it was too late, Batman had killed Joker with his dying breath, Harley screams at her lover's death, Batman falls to his knees at finally ridding of his arch-enemy, he promised that if he finally killed Joker, he would never come back as Gotham's protector and crime fighter, as he returned to Wayne Manor, he hangs his cowl into the costume display to forever abandon his role as Batman.

Later, Bruce sees a SWAT team of police officers surrounding his mansion and found the evidence of his life as Batman as he is given a court date to answer for killing the Joker. In court, Bruce solemnly swears to tell the truth by admitting his role as Batman about how his parents were murdered by Joe Chill in an alley, and that he's been avenging their deaths for years fighting for justice, but Joker stood in his way and that he would ruin his reputation. When Bruce is found guilty for first degree murder, he is sentenced to life in Blackgate Prison to face life, he is escorted to Blackgate, as he knows he will be attacked by a lot of villains he's put there.