So, this thread has proved that basically every comedian who took on dramatic acting were good at it…
Isn’t the famous line “Dying is easy; comedy is hard.”
I have nothing to offer except that I assumed that this thread had been inspired by Volodymyr Zelensky who, regardless of his obvious competence and high skills as a leader, has to be also demonstrating incredible dramatic acting chops.
Um, he’s not acting.
Kinda. I think he is/was mostly a serious actor, but it just so happened that his two early, breakout roles were comedies. So, I’m not sure that he really fits in either thread. 
As I said, “regardless of his obvious competence and high skills as a leader”.
Notwithstanding that I have no doubt that there are ample times when he has to act differently than how he may actually feel. It wasn’t intended as an insult to Zelensky.
I’m pretty sure it’s apocryphal, but that’s the line.
I think there’s something to it though; there seem to be a LOT of comedians/comedic actors who transition into dramatic roles with an unusual level of success. Like to the point where it’s almost a done deal that a comedic actor who plays a dramatic part will do at worst, a workmanlike job of it.
The same isn’t necessarily true in the opposite direction. Some dramatic actors can pull it off (Clooney and Pitt come to mind), but a lot can’t, although it’s becoming more common than in past generations. I mean, Leonardo Di Caprio is funny enough, but can you imagine Charlton Heston in a comedic role?
Well, there was his cameo in Wayne’s World 2:
Peter Sellers demonstrated solid dramatic chops as Chance in Being There.
And Kirsten Dunst and Mark Ruffalo and Tom Wilkinson and …
I really love this movie. Don’t get spoiled!
In radio, Dennis Day, who played Jack Benny’s immature and unintelligent singer for years and years, did at least one dramatic radio role (https://www.oldtimeradiodownloads.com/thriller/suspense/christmas-for-carole-1950-12-21) as a husband driven to crime to get money for his wife’s medical bills. He did a credible job, but it was really difficult for me to take him seriously,since his voice was recognizably silly old Dennis
Art Carney became successful as the clownish Ed Norton in The Honeymooners, but was quite effective in a Twilight Zone episode as a department store Santa. He later won a Best Actor Oscar for Harry and Tonto.
Similarly, Jim and Marian Jordan – Fibber McGee and Molly – gave quite credible performances in the radio drama “Backseat Driver” for Suspense. It was so successful that their roles two years later.
In fact, Carney had a career in radio drama before The Honeymooners came along. He was frequently used in documentary-type programs portraying figures like Franklin Roosevelt and Dwight Eisenhower.
Similarly, Jack Lemmon in Days of Wine and Roses. I’d only seen him as a comedic actor before this.
Years later, Jack Lemmon did a fine dramatic performance in Glengarry Glen Ross.
Izzard was quite good in spy drama Six Minutes to Midnight.
I never thought of Tom Poston ever playing drama, but in an episode of Newhart, his character had to break up with a very sweet woman who loved him more than he loved her. He handled the part of someone desperately not wanting to hurt the person he was hurting with considerable skill - vocally, physically and with the right expressions on his face. Turns out Poston originally studied at the American Academy of Dramatic Arts and had played serious roles before going into comedy with Steve Allen in the mid-1950s.
This was the film where I realized that Tom Hanks could do more than just goofy movies/shows. (And, as an aside, Tom’s portrayal of an advertising guy might have had an effect on me being one… he certainly made it seem fun: “No, I don’t have a half-finished screenplay in my desk drawer. I like writing ads!”)
Mary Tyler Moore in Ordinary People, after appearing as a light comic actress up until then. She was unforgettable as a cold, grieving mother, winning a Golden Glove for her performance.