Which traditionally comedic actor has the best dramatic performance?

I was pondering this after having just watched "Can You Ever Forgive Me?" starring Melissa McCarthy. In that film, I feel she did an amazing job playing against her type as an humble yet flawed woman. Although, my favorite that I can recall is Jim Carrey from "The Truman Show", which started his drama kick that continued with "Man on the Moon" and "Eternal Sunshine".