Okay let me try to explain this as best I can
Hanzo and McCree are aesthetically pleasing together, first off, and who doesn’t love a cowboy/samurai duo? We have a nice height difference, clash of the cultures, completely opposing personalities and they’re within the same age range (McCree is 37, Hanzo is 38). I also have to admit I really dig the fact that Hanzo has his entire left side of himself exposed and McCree has his covered up. Hanzo wears his pride and McCree hides his shame.
Both come from pretty parallel backgrounds. The Shimada Clan and the Deadlock Gang are canonically compared to each other as far as their business is concerned, and both come from those criminal backgrounds. McCree has had his chance to redeem himself, however, since he was picked up by Overwatch and all, unlike Hanzo.
Personality wise, Hanzo is incredibly uptight, stoic, precise and quiet. He’s very serious, and his combat shows it too. Jesse is the complete opposite. He’s very chill, messy, blunt and just… loud. He’s off in the front lines with a loud-ass gun and jingling with all his spurs and knick knacks, and just lets things happen as they do. These kinds of personalities would really compliment each other very well imo. Hanzo needs to loosen up and be more at peace and live in the now; Jesse needs a little more self control and needs to not be so reckless. They’d bring the good out of each other, and the potential for a great dynamic is just right thereee
Another thing to note is the redemption part. Hanzo sees himself as irredeemable and unforgivable. Jesse probably thought the same of himself straight out of Deadlock, but Overwatch gave him an opportunity to fix what he did wrong. Now he’s turned a new leaf and tries to do good. Hanzo is still stuck, and Jesse can -sort of- empathize with him, and help him understand that he can regain his honor. It’s this dynamic that reeeally makes me ship it. Common ground and mutual respect, and Jesse’s drive to help others comes into play to help angsty samurai.
There’s just a lot of potential for these two that can be explored in so many ways, and that’s what fascinates me a lot. I love them and I feel like they’d make a good match, romantic or platonic or worst enemies, idk, doesn’t matter. There may not be any canon interactions between them but it still won’t stop me ;3;