So we have two teams of 15 fighters. Each team has a leader. One team is lead by Captain America, and the other by Ender Wiggin.
Both teams get two weeks prep-time. After those two weeks, the teams fight each other to the bitter end. The fight takes place in Metropolis, and each team starts at another end of the city.
Each team has its own base of operations, in which they plan their strategy and collect their resources for the upcoming fight. Metropolis is covered with cameras (let's assume that they're indestructible, no matter what hits them). The leaders do not take part in the actual fight. They observe the fight via TV monitors that are connected to all the cameras, and they can communicate with their teams and give them orders during the fight. A team wins when each member of the other team is dead.
There is nobody in the city except for the fighters. There are cars (that can be hotwired) parked along the sidewalk and in parking lots, though they're not too common (let's say 15% of the amount of cars you'd find in Metropolis under regular circumstances). During the fight, all fighters can use the rooftops, sewer systems, etc. They cannot leave the city.
Some characters may have specific equipment restrictions and/or unique equipment. Characters without such restrictions/specials, can use whatever equipment they usually have.
2. Jaime Lannister: Mounted on an armored war horse. He's wearing a full set of chainmail and carries a longsword and a shield, and both his hands of course.
3. Mister Freeze
4. Black Widow
5. Hellboy: Carries his Samaritan revolver and some ammo.
6. The Comedian
7. Lara Croft
8. Nightwing: Has a motorcycle.
11. The Punisher
13. Dragonslayer Ornstein (from Dark Souls): Regular form only.
14. Lady Shiva
15. Bane: No Venom at all.
2. Deadshot: Has a high calibur sniper rifle and his silenced hand-mounted pistols, and a large amount of ammo.
3. Dovahkiin (from Skyrim): Nord, restricted to the same gear as in the Skyrim trailer. Can only use melee and ranged weapons, no magic allowed except for the Unrelenting Force (Fus Ro Dah) shout.
5. Killer Croc
7. Ezio Auditore: Restricted to his hidden blades (no poison blade and no pistol), a longsword and a dagger.
8. Kenshi (from Mortal Kombat)
9. Iron Fist
10. Harry Potter: Has a broomstick, though slower than the one he uses in the books/movies (a bit slower than Hawkman). Has a regular wand (not the Elder Wand) and none of the other Deathly Hollows as well. Cannot use the three Unforgivable Curses: Avada Kedavra-the killing curse, Crucio-the Cruciatus curse, inflicts agonizing pain upon the victim, and Imperio-the Imperius curse, forces the victim to do the caster's bidding.
12. John "Soap" Mactavish (from Call of DUty: Modern Warfare): Has a bulletproof military jeep with room for 3 more passengers.
13. Prince Zuko (from Avatar)
14. Invisible Woman
15. Kintaro (from Mortal Kombat)
1. Jaime Lannister: An extremely skilled knight, deadly with a sword, though nothing super-human. Despite having both his hands, he has the mature and responsible personality he had after losing his right hand.
2. Hellboy: A red demon. Has Superhuman strength and endurance, healing factor, slow aging, invulnerable Right Hand of Doom (his right arm is basically an invulnerable hammer with 5 fingers), immunity to fire.
3. Lara Croft: Somewhat of a younger, female Indiana Jones.
4. Dragonslayer Ornstein: A knight in shining armor (literally). Has superhuman speed and agility. Carries a long Dragonslayer Spear that allows him to shoot lightning bolts. Highly resistant to electricity and relatively susceptible to fire. He is one of the Four Knight of Gwyn, which means he was a leader of a large army that has fought Everlasting Dragons and prevailed. It is also rumored that he was the commander of the Four Knights. In other words, he's a very decent battle commander on top of all.
5. Dovahkiin: A Nord warrior in light armor, carries a sword and a shield. The Unrelenting Force shout allows him to send a powerful wave of raw power that throws backward almost everything in its way (it can throw back each one of the other fighters. It would knock back cars as well, though not very effectively. Houses and other structures are unaffected, except maybe for some broken windows and all. The shout can be avoided if you're far/quick enough).
6. Ezio Auditore: A skilled assassin. Extremely skilled in using many kinds of melee weapons, hand-to-hand fighting, stealth and free-running (parkour).
7. Kenshi: An extremely skilled, blind swordsman. Has telekenetic powers and a magical sword.
8. John "Soap" Mactavish: A captain of the British SAS (Special Air Service), highly trained and experienced soldier, can operate various types of fire arms.
9. Prince Zuko: A skilled martial artist and firebender (can manipulate fire).
10. Kintaro: A four-armed brute striped like a tiger. Has superhuman strength and endurance, can breathe fire.
11. Ender Wiggin: A strategic GENIUS, has lead humanity against an alien race and prevailed, that's all that matters for this topic.
So... who would win?