Learn Hardcore Portuguese (Portugal): Todos querem justiça.

todo usually means every or whole/entire, and it often goes with a singular noun:
- todo o dia = all day / the whole day
- todo livro is not the normal way to say every book in standard Portuguese; you would usually say cada livro or todos os livros, depending on the meaning.
todos on its own can work as a pronoun meaning everyone or all (people).

So in Todos querem justiça, todos is standing alone and means everyone.

Why is the verb querem and not quer?

Because the subject todos is third person plural, so the verb has to agree with it.

The verb is querer (to want), in the present tense:

Since todos refers to more than one person grammatically, Portuguese uses querem.