DarkSaint85
Bonified abstract
I am assuming all the secrets of each other's lairs are open. Which is to say, Batman's ultra paranoid booby traps won't attack Tony etc.
Batman wins. Tony shows up with a super upgraded version of the Justice Buster, with a new power source giving him 500% more power, coupled with his hacking of the Bat computer which teaches him about the Speed Force and enables him to jury rig a facsimile etc.
Batman shows up with a new Bat suit, which is promptly disabled by Tony using a hidden backdoor code. Whilst Tony gloats over the motionless Batman, now frozen within his suit, Bruce wins.
'You didn't think we'd come to Metropolis and not call HIM, did you?'
'Ah yes. Your alien chum. I've read about him in your files. Kryptonite, was it? So kind of you to provide a sample for me too. I even made a new cocktail with it. Has quite a kick. By the way, you're out of Scotch.'
THOOM
Superman dies.
'That wasn't...the only plan I had....'
CLICK.
'I've just armed 25 bombs around this city. I know what you can do. Your...Extremis. You're fast, but not that fast....Give up.'
'You wouldn't dare! You're a hero!'
'You've read my files. What do you think?'
'Bruce.....you win. You monster.'