system
Given the following post, respond as if you're commenting on Reddit:
human
Who would win in a fight between the Justice League and The Avengers?

I overheard some scientists talking about this new dimension they found called Earth-7642. Apparently there's another group of superheros. If humanity depended on our supers versus theirs, do they even have a chance? I mean, we have Batman.
gpt
Let's base this off of character abilities and we'll start with the two most current rosters. For the Avengers main roster (Marvel Now!) we have: Cannonball, Sunspot, Manifold, Shang-Chi, Captain Universe, Hyperion, and Spider-man. For the Justice League main roster (New 52) we have: Superman, Batman, Wonder Woman, Green Lantern, Aquaman, the Flash, and Cyborg.

It could be very easy to give the advantage to the League, they certainly seem to have a lot of firepower with Superman, Green Lantern, and Cyborg alone. As well as a considerable amount of backup and utility. This team of Avengers seems to be made up of people we have never heard of. Conflict between them and ultimately who wins will eventually boil down to two men. But before we get to that, lets see who outs whom shall we?

The first casualty of this fight would ultimately be Aquaman. His strength and durability does him little good when he is easily dehydrated and rendered useless without a close source of water courtesy of Susnpot. Sunspot is ultimately contained and sent packing by the powers of the Lantern. Next out would probably be Wonder Woman, though she is powerful she cannot match Captain Universe. The two women would surely fight it out for quite some time before Captain Universe wins out with telekinesis and the unpredictable Uni-Power. However Captain Universe is also easily contained and dealt away with by Green Lantern. Our next big fight would be between Spider-man and Cyborg. With technology on his side Cyborg could gain an early advantage. Until he realizes that this is not the wise-cracking Peter Parker but instead the diabolical psyche of Dr. Otto Octavius with all of the power and none of the responsibility Cyborg is destroyed by a collapsing building. However our web-slinger is not expecting the attack from the shadows that drops him and renders him unconscious. The Batman learned by watching the fight that Spidey could sense an attack coming. But what if the attack wasn't pre-meditated and even caught the attacker by surprise? A gamble that pays off for the Dark Knight. This leads us to a knock-down drag-out fight between two martial arts masters, Batman and Shang-Chi.

As the two hand-to-hand beasts battle it out we turn our attention to Cannonball. Sam tries to keep up with Barry as the Flash races around the scene helping his teammates. Unfortunately the Scarlet Speedster is in a class all his own. Cannonball loses his focus in his frustration and drops his protective shield just long enough to get driven into a building on a tight hairpin turn. Flash enjoys his victory, but only briefly. As he takes off to assist Batman he finds himself running past.....himself. Confused he attempts to stop to see what just happened only to realize that he can't stop. The reality bending teleporter Manifold has trapped the Flash in a Mobius Strip of reality, forcing him to speed along until he starves. This is when the Man of Steel gets involved, crashing down on Manifold before he can teleport away. Smasher now swoops in to avenge her fallen teammate. Using her goggles to absorb superhuman durability and increases her strength exponentially. Swinging for the fences she begins to duke it out with the Last Son of Krypton. Green Lantern awaits his time to strike and contain Smasher, he's so focused he doesn't realize he is being watched from outside Earth's atmosphere. Before anyone knows what happened The Emerald Knight is gone, and only a cloud of dust remains. Smasher's durability cannot hold up to Superman, especially once her goggles are destroyed. Superman stands victorious, but only momentarily.

Batman and Shang-Chi fight hard and long before both of them ultimately succumb to exhaustion. They are both human after all. 

Superman surveys the carnage and stands proudly, the last man standing. That is until he is blindsided by an unknown force seemingly from space. From the rubble he stares up into the eyes of Mark Milton, Hyperion an entity not too unlike himself. This is where the true battle takes place, a fight for the ages as these two godlike beings go at it without stopping for days. But Hyperion realizes something, though still formidable his opponent loses some of his umph when the sun goes down. On the 20th day Hyperion seizes his chance when the sun goes down and no moon rises. Using all of his strength and effort Hyperion launches himself and the Man of Tomorrow into space and out past the edge of our solar system. With no means of recharging, the fight soon turns in the favor of Hyperion. After dispatching his foe, Mark Milton stares into the cold reaches of space and contemplates the questions that will come to plague him for his whole existence: What is his purpose? And can he die?