Sombra simultaneously destroys the game and holds it together
Without her literally WHAT would people do about doom/ball? Nothing. You’d just lose.
But also, in order to keep them in check (because I’m sick of people saying counterplay = being a counter, she doesn’t counter them, she’s just the ONLY dps with any option to fight back meaningfully and dive tanks call that a “counter) she must also be able to keep other tanks “in check”
Sombra doesn’t counter doom/ball, she can be played around and with team play her effects can be mitigated enough to be handled
She DOES counter sigma/rein/ram/hog/Mauga by turning off their life support and they don’t have kits to immediately save themselves after a crucial cooldown was removed from them or in reins case he just has nothing he can do back
She counters them because the completely dictates when and where they can do things and they can’t punish her for it. Unlike doom and ball who can go right back to what they were doing, or have the mobility to select different plays to force sombra to act a certain way- or even to just be taking all her focus so they aren’t getting picks.
And again, other tanks
A: lack the flexibility to protect their team from sombra, thus effectually making her a counter
B: lack the flexibility to rehabilitate themselves in time after being hacked, offend seriously increasing the chances of them dying, and even if they don’t, the enemy dps has just taken most of the tanks resources and attention easily
Sometimes counters aren’t about “makes it possible to kill”, that’s just the game. Sombra plays the game with doom/ball.
But counters are ALWAYS things like- these hero’s (most tanks) literally can’t interact with these very dangerous predicaments they are forcibly placed into and must frantically try to survive and do their job without having any real input about the situation (like a junk/sym vs pharah)