The award for best comedic actor in a dramatic performance goes to....

Jack Lemmon in DAYS OF WINE AND ROSES

Your pick?

It may not be the best,but it was my first thought.

His role in the movie made me emotional

I think lots of comedians can step out of the box,because lots of them are lonely and or melancholic. That and they observe life, for a living.

Sure he was playing a comedian but it was still a great dramatic performance.

The first time I saw him in a dramatic role (elements of comedy, for sure, but light years from Mork) was Moscow On The Hudson, a relatively obscure film that I think deserves far more attention. He's since nailed some great dramatic roles, including playing a couple of out-and-out sociopaths.

Of the other two mentioned so far, I wouldn't have named either because I tend to associate them less with outright comedy. That'd be wrong, on my part, because not only are Tom Hanks and the late-great Jack Lemmon skilled actors in more dramatic roles but they're greatly adept at comedy, and most people will agree that comedy is NOT inherently an easy thing to pull off well. Yeah, I think a lot of the strength these people (and Jim Carrey, Michael Keaton, and others) bring to 'straight' dramatic roles is the observational mindset that served them well in comedy.

I think it's worth noting that Robin Williams (Julliard graduate, roommate of Christopher Reeve), Tom Hanks, and Jack Lemmon were all formally trained as dramatic actors at the outset. Playing more serious roles, and doing so convincingly, is just another facet of the prodigious talent each has.