In many ways, Blizzard's handling of Sombra post-release (and I do emphasize "post"). Their first stealth hero was released to underwhelming reception, with many people thinking she wasn't strong enough. But, learning from their mistakes with Ana, Blizzard didn't immediately give her a huge buff immediately thrusting her into the mainstay of the meta such that she'd need a nerf. Instead, Blizzard waited for people to get the hang of her, and rolled out some tiny, incremental improvements in patch 1.7 that made her more viable in all situations.
But, while many people still think she's underpowered, we now know that she could have needed some huge nerfs right out of the gate. Responding to a forum suggestion/question about a potential change to Sombra, Overwatch Principal Designer Geoff Goodman she light on two abilities that were seriously considered and tested for the hacker/assassin.
1. Turret Hacking
Sombra would have the ability to hack enemy turrets and turn them against the opposing team. This would mainly affect Torbjorn and potentially Symmetra. Of course, this had some major balance issues and unforeseen ramifications. As Goodman puts it, "it felt so punishing that [Torbjorns] would just switch instantly if a Sombra appeared on the enemy team. Teammates would rage at Torbs if they ever got killed by his turret, etc."
2. Objective Hacking
From the forums: "She originally had the ability to directly hack objectives like capture points and payloads. If she hacked those, it would create a hologram of a player on it which would act as if she was standing on it. The enemy team couldn't destroy it and just had to contest the objective as long as the hologram lasted.
Goodman said this ended up being "super frustrating" to the enemy team, and made it so that's all Sombra would do the whole game.
So we could have very easily had a turret-hacking, objective-camping stealth hero that would have instantly removed the viability of another. I think no matter how Sombra turns out with future buffs or nerfs, we can all be thankful she got reworked pre-release.
Now, if they do another damn ARG for Doomfist, I propose a march on Blizzard HQ.