Lol, that is almost a guaranteed cheater. That amount of damage consistently in all matches is a giveaway. There are exceptions of course when someone is hardpocketed and not pressured for an entire game, but I am almost certain in this case you queued with a cheater. 30k in round one is bonkers, especially on Dva.
There are many ways to spot a cheater in comp. Consistency is often the best giveaway. Machines are consistent; humans are not. Humans are more consistent in short bursts, not for an entire game. If you see someone consistently making miracle shots, almost never missing headshots, even difficult ones, especially on high-mobility heroes, they are usually cheating.
If you can never surprise anyone, even if you see them first, or if someone is always waiting for you when you flank, they are usually wallhacking. Enemies that always manage to do superflanks on your team and no one ever spots them, especially when they are playing low-mobility characters like Cassidy, Bastion, etc., are usually wallhacking.
Gamesense not matching mechanical skill - poor positioning, movement, awareness, bad ability usage, yet perfect or near-perfect aim. Cheating Cassidy trying to headshot people from Widow’s range and doing tickle damage even with his aimbot because he has no gamesense, cheating Tracer dueling people from medium to long range. Aim pros that never miss a shot dying like flies to simple Junk spam in a corridor because they have zero gamesense.
Ridiculous amounts of damage in a short amount of time, especially on low-damage heroes. Supports outdamaging DPS 2-3x when said DPS are playing well and are not underperforming. DPS getting their ult in like 30-40 seconds after the match starts. DPS that finish a quick round one with 18-20k+ damage while not being pocketed by a damage-boosting Mercy.
Spamming movement abilities like crazy yet still hitting every single shot. You can’t have perfect aim while dodging like crazy at the same time, especially in a game with no movement acceleration like OW2. You can try to somewhat compensate and it is a skill that is developed through a long amount of time and still it is not perfect. You either sacrifice part of your aim for better evasion or part of your movement for better aim. If you see, for example, a 76 running, jumping around doing quick 180-360 while still lasering everyone, they are cheating.
Perfect ability usage without LOS. Enemies perfectly dodging your stun or other abilities without seeing them coming or perfectly landing such abilities on you when they don’t even see you. Anas that land those lucky sleep darts across the map without LOS, Anas consistently landing SDs on high-mobility characters like flyers, Genjis, and Tracers. Tanks that always eat your abilities without fail like D.Vas and Sigmas. Genjis that do magic dash combos behind corners or perfect last millisecond deflects. Shield-botting Rein’s doing 180s to block an SD they did not see coming.
Other or minor tells:
Screen shaking like crazy every time you watch their killcams, choppy, fixated machine-like aim, like everyone who plays this game has last-stage Parkinson’s or something.
Your team, especially your tank, getting hard-countered before the match even starts. (3 or more hard counters)
Attention-seeking in chat, being awfully polite and chatty from the start of the game.
Suspicious profiles, when you know, you know.
This is actually just a very short summary tbh, I hope this helps.