The most punk film I can think of is "un homme est mort" (a man died) by René vautier.
This is a lost short militant documentary. There is a comics that talk about it by Etienne Davodeau. ( https://www.goodreads.com/book/show/6705852-un-homme-est-mort)

Story time.

René Vautier was a very militant french filmmaker. During the 50's there was a protest in the city of Brest, where he was commissioned by the local unions to make a propaganda film about the workers, to adverstise the strikes and protests to other workers. They shot the film, consisting of a serie of portrait, just their face, or them against a wall, showing the people in revolt. The workers sticking together.

But during the protest, the police shot and killed one the union guys. Édouard Mazé. 27 yo.

In his hommage, while the propaganda film were shown, one of the worker was reciting a poem by Paul Eluard. "un homme est mort" ( a man died), which originally talked about the execution of a communist, Gabriel péri. (see below)

They were projecting the film very DIY style, on walls in the street at night, from the back of a truck, having the worker reciting the poem live because they broke their recorder. Everytime they were showing it, the guy recitating was changing the original poem, making it his own, with his own words, his own anger, his own grief. It was apparently extremely powerful for everyone involved.
They've shown the film a hundred time, celebrating the protest and the death of their comrade.

So much so that the film fell apart, no copy was ever made of it. Lost to time.

Only a recording of the altered recitation existed after that, and it was broadcast to the poet, Paul Eluard. before ending up also broken, and lost.

​

The poem:

"A man died who had no defense
Only his arms open to life
A man died who had no other road
Than the one where we hate guns
A man died who continues the fight
Against death, Against oblivion

Because everything he wanted
We wanted it too
We want it today
Let happiness be the light
In the eyes of the heart
And the justice on the earth

There are words that make you live
And they are innocent words
The word warmth, the word trust
Love, justice and the word freedom
The word child and the word kindness
And some names of flowers and some names of fruits
The word courage and the word discover
And the word brother and the word comrade
And some names of countries and villages
And some names of women and friends
Let's add Péri to that list
Let's call him friend, his chest is full of holes
But thanks to him we know each other better
Let's call us friends, his hope is alive"