Probably the goriest part of the movie. You’ll know when it’s about to happen.

Not exactly squashed but one character's head gets severely mutilated by an accident involving a utility pole and another character smashes his head on a desk repeatedly.

Oberyn Martell's head is crushed by the Mountain.

A car runs over a man's head as he lies in the road. Only the characters in the car's reactions are shown (they don't see what happened and assume it's a speed bump), but the noise is quite graphic.

The back of someone's head is hit/smashed with a large rock; I would not describe it as "squashed". The victim survives. We see the rock come down, and blood, but we don't see the injury directly.

Pennywise manipulates their body throughout, including squishing their head flat. Twoards the end their head also deflates like a baloon.

One character had his head bashed in by a metal ball, although I don't think there was any gore shown, only blood.

Two characters in chapter 3 die from their heads being smashed with a hammer/mallet. The scenes are bloody, but their heads aren't mutilated.

Not so much squashed. More beaten against a wall.

A character is crushed to death.

Someone's head get bashed in, it's off camera but there is blood spatter

Two heroic characters are seen having their heads bashed in with a baseball bat. The scene is gory and disturbing

There's a very graphic scene where a man squashes his wife's head in with his bare hands.

EP 7, 19:40 SPOILER ALERT A head explodes. There's blood and they show the body fallen without head and people dirty around them.

There is NO literal head squishing in the movie. Thor's head is seized and threatened to be squished, but THAT IS ALL.

Mina’s head is crushed during the attack on Trost in season 1. MANGA SPOILERS: Zofia is crushed by a rock during the massacre of Liberio. Udo is trampled to death by a panicked crowd during the same event.

Multiple unnamed enemies are hit in the face with a bat/mallet/gun, and blood splatter is shown, but the aftermath is not visible

Someone's head is crushed with an ATM machine.

A character's face gets bashed in, very graphically!, at the end of the movie.

lots of episodes have descriptions of violence against other people but the one that sticks out to me for this particular category is mag 80, where a character is beaten to death with a pipe on tape

There's a fair amount of decapitation which leads to heads being kicked and carried around

Not on screen, but people are shown with severe head injuries

Hand man go bye bye

Roanoke

Like almost every time you get a melee kill

At the end by Adam

No humans are shown losing their heads or having their heads destroyed, though some are implied to. But superhuman characters that have the ability to regenerate their (human looking) bodies get their heads destroyed and regrow them a number of times, most graphically in Episode 13 "Beasts of Dublith", this one in particular is shocking and happens suddenly and without warning

This happens multiple times, to multiple characters, in multiple episodes, in gory detail.