My most recent go-to example is Melissa Barrera.

Her performances in Scream and Scream VI are completely night and day, IMO.

I almost completely wrote her off after Scream, where I often found myself cringing anytime she spoke or tried to emote. She took me out of nearly every scene she was involved in, save for certain segments of the finale.

While she still had some weak moments in Scream VI, I was finally able to see Sam as a character, as opposed to an actress desperately and unsuccessfully trying to portray one. Better yet, I actually liked and sympathized with Sam. Hell, I rooted for her.

Major respect to Barrera for doing whatever she did to step it up.