From playing these characters, these are my best guesses. This is also from a gameplay perspective, minus ultimate usage, as most engagements revolve around the heroes primary abilities.
McCree vs Caldarius = McCree flashbangs and fans the hammer, Caldarius dead. Caldarius could blind McCree and flee, but McCrees shots would most likely dispose Caldarius quickly if he were to return.
Attikus vs Winston = Attikus’s punches would take Winston down faster than Winstons electricity could get through Attikus’s health.
Ambra vs Mercy = on offensive terms, Ambra would win. A sunspot healing Ambra and damaging Mercy while Ambra hits mercy with her beam, then finishing mercy off with scorching strikes. Mercy would struggle to land hits on Ambra or even kill her during that.
Deande’s vs Sombra = They both initiate from stealth. Sombra attempts to hack Deande and succeeds. Deande cannot use any abilities. Sombra mows her down with her SMG. Deande manages to disrupt her hack, she gets close enough to continue disrupting her, Deande’s wins. I consider it a draw.
Reyna vs Zarya = Zarya puts up a barrier to absorb all incoming damage from Reyna. Her plasma pulse gradually takes the shield down, but by then it’s too late. Reyna is unable to obtain an over shield without an ally. Zarya’s beam melts her before she can do anything.
Pendles vs Genji = Pendles is slow outside of stealth, this gives Genji the advantage. He uses his shuriken to take him out at a range, and dashes through Pendles to secure the kill. Genji uses his mobility to evade Pendles’s Melee attacks and his throwing star is to slow to keep up with Genji’s movements.
Toby vs D.Va = D.Va’s Defense matrix can’t absorb Toby’s rail blasts, similar to Zarya’s beam attack. Toby, however, suffers from a large hit box. D.Va uses her jet boosters to close the gap between her and Toby. She uses her shotgun blasters to quickly take Toby down.
Montana vs Reinhardt = Montana burns through Reinhardts shield as Reinhardt closes the gap between them. He continues firing while Rienhardt takes swings at him. With Montanas constant fire still on Reinhardt and swings still being delivered, they both happen to die at the same time. I consider them a draw.
OM vs Soldier 76 = soldier 76 places a biotic field to patch him up while OM tries to take his health down with his rifle. Soldier then releases helix rockets and fire from his own rifle, to quickly burst down OM
Benedict vs Pharah = this is a difficult one. Pharah can use her superior movement to her advantage, but if Benedict locks on with Hawkeye, she is done for. Depending on the situation, I would call it a draw.
Galilea vs Reaper = Reaper can use his movement options to his advantage. Flanking Galilea and dealing massive damage. Not before she lands a stun and deals massive damage in return. He uses wraith form to flee and teleports to a different position to prepare for another flank attack. He manages to flank her again and finish her off. Could be considered a draw depending on how Galilea reacts.
Ghalt vs Roaghog = Ghalt has moderate health. If Roadhog lands a hook on Ghalt, he is most likely done for. If Ghalt lands a hook, roadhog will most likely recover with his “take a breather” ability to gain health back, and while in range, blast Ghalt with his shotgun.
Ernest vs Junkrat = Junkrats trap and mine would serve to pin Ernest down in place. Ernest lacks movement options so once he becomes ensnared, Junkrats bombs and trap will make easy work of him. Junkrats bombs would easily destroy Ernest’s power egg and leave him vulnerable. Junkrat could use his mine to launch himself into the air and gain a height advantage over Ernest.
Thorn vs Hanzo = Hanzo…those aren’t arrows he fires, they are logs. If he even catches a glimpse of Thorns head, snip, elimination. Scatter arrow would also make quick work of her. Thorn may be able to jump high, but Hanzo can climb walks and detect enemies through walls. Thorns abilities could possibly burst him down, if she’s even survives a log to the head that is.
Boldur vs Torbjorn = bolder without a doubt. His shield and health pool would be able to soak up the turrets damage, allowing him to get close enough to Torbjorn and kill him. Torbjorns damage most likely would do enough in time to stop bolder. Also take boldurdash into account with over shield and rage.
Kelvin vs Mei = an odd one. Since these match ups are based on gameplay, I would consider this a draw. She could freeze Kelvin, yes, but Kelvin can gain shields from ability use and absorb damaged because of his health pool. Mei’s icicles don’t exactly deal massive damage so he could melee her to death. Her ice wall could block him out while she recovers, and she can recover health from her ice form, but he would eventually kill her, or she would eventually kill him.
Mellka vs Tracer = If Mellka lands venom on tracer, she is as good as dead because of her very low health pool. If tracer can successfully flank Mellka hard enough, her health would drop quickly. I’d consider this a draw.
Alani vs Zenyatta = two of my favourite characters, interesting. She isn’t the toughest character, so if zenyatta successfully lands orbs of destruction on her while she is discorded, she will drop quickly. If she lands enough hits to kill zenyatta, she would win. But I believe Zenyatta’s damage output would be far greater over all. He would most likely win.
Marquis vs Widowmaker = a battle of the snipers? Widowmaker hands down. He is a weak target, and she is built to react quickly she also has an avantage to movement with her grappling hook. He would die in an instant. Marquis would have to set up his owls and distortion field, that is time he CAN’T afford while he is in Widowmakers sights.
Kleese vs Symmetra = Symmetra builds damage over time with her primary fire that locks on. Klees’s lock on is consistent damage. He would dispose of Symmettra quickly, as a portion of her health is shields. Something Kleese specialises in restoring and destroying.
ISIC vs Bastion = ISIC’s deflecting rotating wards would only do so much in comparison to Genji’s deflect. Bastion would tear down ISIC’s rotating wards and proceed to destroy ISIC himself. ISIC’s shield would also drop quickly and his primary fire wouldn’t be powerful enough to kill Bastion before Bastion kills him.
Kid Ultra vs Lucio = Lucio can constantly regenerate his own health, but if Kid ultra mixes his bolas with his burst primary fire, he could take down Lucio quickly. Lucio’s primary fire has the potential to kill Kid Ultra as well, or he could just push him off the nearest ledge. I’d call this one a draw.
