Another movie like this

The mini-series of On The Beach was another gut punch. It was about the survivors of the immediate war dealing with the radiation spreading out over the earth via the weather... radiation that will eventually kill most if not all of humanity as well as all other life on the planet.

There's a scene where two parents decide to kill themselves and their young children so that they don't have to deal with the horror that coming. The parents bleakly give the pills to the children and then lie down with them on the bed together to comfort them in their final minutes. Probably the single most depressing scene I have ever seen in a movie.

Edited from my Quora post:
British Post Apocalypse
No Blade of Grass – 1970 - If The Day of the Triffids originated as a “cozy catastrophe” novel, this (based on a John Christopher novel) is an attempt to make a distinctly non-cozy catastrophe. A disease of grasses including all wheat and rice causes worldwide famine and the fall of civilization. The protagonist will lead his followers to some sort of refuge at any cost. A rather laughable biker gang, is the main weakness of the film

Humor of the Apocalypse
The Bed Sitting Room – 1969 - Well, the bombs have fallen and Britain is a radioactive wasteland, but ‘ya gotta laugh… This is a surreal, satirical masterpiece. This comes from the same year and the same gene pool that spawned Monty Python’s Flying Circus.

Le Dernier Combat – 1983 - French. A violent, misanthropic Looney Tunes epic, brought to live-action black and white reality. But it is funny.

Delicatessen – 1991 - French. A gentle, quirky comedy about murder and cannibalism in the wake of apocalypse.

Slit Your Wrists
Letters from a Dead Man - Pisma Myortvogo Cheloveka – 1986 – Russian. A ghastly, if slow, picture of survivors in the aftermath of a nuclear war. Not as straightforward as the British film Threads (1984) but at least equally bleak.

O-Bi O-Ba - The End Of Civilization – 1985 - Polish. This is set in a huge, overpopulated bunker where survivors of a nuclear war are being fed a starvation diet and kept occupied as they await the arrival of The Ark… which will rescue them…

La Jetee – 1962 – A short and barely a film at all (a sequence of still images that is set in motion only for an instant), this remarkable Chris Marker masterpiece is the basis for 12 Monkeys.

Late August at the Hotel Ozone - Konec Srpna v Hotelu Ozon (original title) – 1967 - Czech. A group of savage young women are led across post-apocalypse countryside by an older woman, who is the only one born before the end of civilization. Not as charming and gentle as, say, The Road Warrior.

The Afterman – 1985 - Belgian. An illiterate man, unable even to speak, emerges from years in a bomb shelter to a world that is ruined and sleazy and very, very unpleasant. This one contains a lot of rape and even bestiality. What is it about Belgians and pigs?

Long list hear https://www.imdb.com/list/ls009625336/