Congratulations! You win the right to write the following events..
DC and Marvel have decided to do another crossover.
A certifiable writer (say, Mark Waid) depicts the storylines, but as far as the actual 'meat' of the action, YOU've been picked to portray it.
Remember, this is an official storyline, and that implies a certain amount of respect for the characters involved. You may like a certain character, sure, but should he win? You can be a Wonder Woman fan but, if she were to face Thanos in a comic, deep down you probably know that she can't beat him straight up. You can work around that, as far as it's in character, and also as long as it doesn't deviate too much from the setting of the scenario (so she doesn't randomly call Zeus or the Godwave or whatever shit comic fans wouldn't actually enjoy reading about).
Be as specific as you'd like about how the fight would play out. Dialogue included. Don't drag it too far, though. It can also end inconclusively, but don't be a b*tch. Remember, you have like 5 pages each (and that's for fights that are very important. Choose which ones you think those are)
With that said...
Thor/Wonder Woman
Context:
Odin killed Hyppolita to prevent war with the amazonians and possibly Olympus. He is in Odin sleep, and this is Diana's chance to get revenge. Thor is the only one standing over him. Sword, lasso and shield are on her. Thor knows her intentions.
Superman/Flash race
Context: They're on the edge of the Universe. An artifact is sent backwards towards the center the Universe at unimaginable speeds - once it reaches it, everything will implode, taking the whole of creation with it. Superman can't fly, otherwise his gravity manipulation will just push him further towards the edge of the Universe, so he has to run. Due to the speed-force, an energy 'road' is made in their proximity and they can also interact with eachother. Whoever touches the artifact will die. They both know this, so are trying to sacrifice themselves for the other. Go.
Black Adam vs Hulk
Context: Due to the Superman/Flash race, time/space is mangled, the Warbound arrive in Khandaq just as Osiris and Isis are killed by the Horsemen. Black Adam gets back and, thinking that they're the ones that killed his loved ones, engages and kills them all. Hulk just lands, seeing them all dead. Adam thinks Hulk is the last horseman. Both are grieving too much for words.
Superman vs Thanos
Context: Saturn. Thanos has to fingerprint-activate a device that converts DC's solar system into sustenance for Galactus, who desperately needs it so that he can go back in the Marvel Universe. If he does not, the Universal concepts (such as Death) will fade out of existence within the MU. The rest of the population within the Marvel Universe will be completly fine, though. Superman stands between him and the device. To get here, Thanos killed Batman and Wonder Woman.
Wolverine vs Aquaman
Context: Wolverine killed Mera, who he thought was about to invade with Atlantis' army and kill thousands of the population (he was in fact manipulated by Black Manta to believe so). Aquaman finds this out from a nearby fish (lol). He goes and searches for Wolverine. Jean cuts his path and probes him telepathically. Unprepared for the rage inside him, she was put into a coma when she telepathically tried to get inside his head. Wolverine thinks Aquaman hurt her as retaliation.
Gladiator vs Hal Jordan
Context: The Imperial Guard think Hal and his fellow lanterns have intervened in affairs out of their jurisdiction. Hal says they have no jurisdiction. While the other Guards/Green Lanterns are engaged, Hal and Gladiator go at it solo.
Black Bolt vs Martian Manhunter
Context: J'onn infiltrates Attilan, manipulated by Maximus, thinking the Terrigen Mist is responsable for the fire-based weakness and subsequent wiping of his race. He wants to dispose it. Black Bolt arrives, and can't allow him to do that.
Cyborg Superman vs Sentry
Context: Henshaw thinks Sentry throwing the Void into the sun is what made him the way he is. As a result, he kills Lindy. Sentry enters the room just as it happens.
Superman (Doom) vs Thor/Hulk
Context: Doom takes advantage of Superman being weakened by kryptonite to swap their minds. He regains his full strength and tries to get the ultimate nullified to restart the Universe and set things the way he wants them. The Fantastic Four are gone, so the Avengers stand in his way - only Doom nearly kills them all, baring Hulk and Thor who arrive at the scene. Doom looks at them and his eyes go red.
I'll do more later..