There's nothing says artistic bravery like an actor turning their back on their established brand and trying to do something different. Like leopards changing their spots, it's both unexpected and can have huge impact.
It doesn't always work out, of course. Famously, for Hitchcock's classic Suspicion, Cary Grant was initially cast to play the murderer, but the studio insisted that the public wouldn't accept him as a murderer so they changed it. And even when actors are actually cast in these transformative roles, it doesn't always last: Macaulay Culkin tried to break out from Home Alone's image by playing a psychopath in The Good Son and it tanked. He went back to playing the same characters for a year and then disappeared.
Vince Vaughn tried it too with Psycho and it didn't stick because that film sucked, but he's had more recent success with serious, unhinged roles, so there's hope for him yet.
Those morality tales aren't the whole story, of course and there are a number of actors who have managed to successfully break expectations and go against type to fashion themselves a broader career. Adam Sandler isn't among them though, because he sometimes proves he CAN do against type and then goes back to it like some sort of sadist.
More interesting are the ones who don't just break their typecasting, but smash it into tiny pieces with extreme choices...
It's almost a cliche to say, but Tom Hanks was the ultimate everyman actor. He has solid, dependable charisma, can add heart to even slightly dislikeable character types and he is pretty much the greatest romantic comedy lead of modern times.
Basically, cinema-goers love him, right across the hero spectrum (from astronauts to cowboy toys to police bachelors).
How He Broke It
Though he's not a villain in the strictest sense, the idea of Hanks playing a mob assassin is still wildly out of his wheelhouse. He'd done complexity before, but he'd never abandoned his core morality and integrity that had developed out of his earlier snarky comedic heroes image. This was the very definition of subversion and it worked incredibly well.
Since then, more morally dubious roles have sneaked in, but this feels more like Hanks proving he can do it rather than trying to make a new career for himself.