By lore, TF2 has Canteens, which can give them invulnerability and triple damage. Medic can also revive his teammates in MVM which is part of the lore. Besides, Overwatch is 1 man down because Sombra is utterly useless because she can't hack shit. If you say Engi's sentry, it's old machinery I don't think you can hack. The most modern technology I can think Engineer has in his sentries is a radio for his wrangler. Spy however, has a lot of things he can do, he is sombra but better because of his sapper, which in MVM can disable robots, kinda f**king over half of all over watch characters because they are part electronic. So the fight becomes who can wear the other team out first. Because both of them can keep reviving (I'm giving Overwatch Mercy here because they don't have a healer for some reason). Which I think TF2 will, because they are all too mentally ill to give up.