Symmetra is the strongest hero by lore. I think Jeff confirmed this. She is the best light engineer there ever was, and in the lore she can create anything she wants.
She could nuke the planet if she wanted, but she doesn’t. She could wipe out humanity and become the new god of earth with that power.
The Vishkar as an organization might have access to much stronger city buster level weapons but all we know Sym can do on her own is make small scale structures for personal use. It’s still pretty strong but nowhere near “Nuke the planet” level.
He can easily take out normal humans with his bare hands and imo should be higher but I don’t think he stacks up against the inhuman (sometimes literally) freaks that make up some OW characters.
Doomfist can (allegedly) level buildings, Sigma controls gravity, Reaper is a vampire vape cloud, Winston is a super gorilla and even a normal gorilla would probably kick Hogs bum in unarmed combat.
She’s actually the leader of talon disguised as a scientist who actually died in Ecopoint: Antartica. She just stole the identity to fool people and is now waiting for the opportune moment to reveal herself as the supreme goddess of suffering and death.
Vishkar is a BUILDING company, how would they have access to weapons? Even with Talon’s help, they would have a lot of trouble explaining anything as big as a basic rocket-launcher.