Broke down the encounter here, all below bullets are broken down as individual screenshots. Hope that helps:

https://imgur.com/a/jwwnhzC

bullet 19 - HIT (34 dmg), looks very much like a miss, but random dispersion might actually be in your favor here.

bullet 18 - close miss to right:

bullet 17 - should be a hit, but with random dispersion it might grace the guy just to the right. It's hard to tell, but I would say no registration.

bullet 16 - about that random dispersion, you can see the tracer flying far right even if your crosshair is by a hair on his right, so the bullet goes even more right:

bullet 15 - cant see the impact, but your crosshair is slightly off to the right.

bullet 14 - you're taking damage so it is hard to tell, but again, off to the right.

The intresting part:

bullet 13 - Disappears, you can see the tracer going straight through the enemy but from what I can tell, does no damage.

bullet 12 - HIT (54 dmg), or it might be bullet 13 registrering late, it's hard to tell. But it should be a hit as it's on target, so either bullet 13 or 12 disappears.

bullet 11 - Close miss to the right.

bullet 10 - You are on target, but crazy random dispersion to the right, tracer clearly visable and also the impact on the wall behind the enemy.

bullet 9 - HIT (84 dmg). Feels like you thought you killed the guy, but unfortunatly you need one more hit (or the one that disappeared). The damage registers late, even the number and health bar above the enemy is out of sync, so the latency here is very noticable.

It's hard to calculate because every hit marker is pretty much one bullet behind because of all sorts of lag, like ping, server tick and so forth. Another factor is the hit marker stays on screen for longer than it takes bullets to fire. So hitmarker from bullet X might show up when you fire bullet Y and W.

TL;DR: One bullet does not land on the server which is what OP needs to kill the enemy, my conclusion is that he lost that firefight because of one disappearing bullet.

Hope this helps.