Christian Bale in Hostiles and Gary Oldman in Leon spring to mind.
Was watching Grey's Anatomy the other day though (a few years behind) and there's a chap called Giacomo Gianniotti playing a character called DeLuca who absolute stole this scene where he's been struggling with bi-polar and has a mental breakdown. One of the best performances I've watched, and it wasn't even a movie.
In fact, I went off to find it:
https://youtu.be/jTwLrXHef3E?si=lDV5wyMlIbn6WSip
Context: He's a doctor whose Italian dad suffers from extreme mania. Story builds up over a number of episodes that the guy is slowly going the same way, which comes to a head when a patient comes in and he suspects the girl is being child-trafficked.
Of course, no body believes him because of his bi-polar, which triggers the meltdown.
The little cracks in his voice and the way he knows he's not right in the head, but he is actually right here...his sister's the one in the pink, front row. The look she gives him too!