Won for: Mary, Precious (2009)
If there was any role that Mo'Nique would win an Oscar for, it was this one. Prior to Precious in 2009, she was known primarily for her standup and roles in comedy films like Soul Plane (2004) and Welcome Home Roscoe Jenkins (2008). She also took a hiatus from films since then, with her first major role since Precious being Blackbird in 2014.
Won for: Minny Jackson, The Help (2011)
Going out on a limb to say that her best role is yet to come. At the time, The Help was decried as another case of "black people can only win awards when they're playing maids and butlers." But before winning the Oscar, Spencer spent about 15 years as a character actor in minor film and TV roles, in everything from Being John Malkovich to Big Momma's House. Now that she's been attached to higher profile projects, there's a solid chance that a leading actress Oscar is in her future.