Madara

[JasonTheArgonaut]

Orochimaru & Tobi were master manipulators but Madara is on another level
Obito as a kid couldn't get home fast enough
and now he's all like ****k the world

Madara messed him up pretty bad

 

[Simple Math]

no madara = obito would't even have been alive

 

[Awkward Linguist]

If Madara wasn't there, then obito wouldda been a goner.

 

[JasonTheArgonaut]

yeah but i think he's more or less forced because if he doesn't listen zetsu just destroys him

 

[Pradhan Tuna]

No matter how much a person brain washes.. It all depends on the one if he wants to change or not ..
So madara has played a role but mainly its Obito who got persuaded.