Learn Italian: Avremmo voluto mostrare più solidarietà e coesione a tutti loro. - We would have liked to show more solidarity and cohesion to all of them.

In Italian, when the quantifier tutto is followed by a stressed personal pronoun (like noi, voi, or loro), you do not use the preposition di ("of") or a definite article. You simply place the pronoun directly after the quantifier, making sure tutto matches the gender and number of the pronoun: tutti loro.

Why does this sentence use avremmo (from avere) instead of saremmo (from essere) for the conditional perfect?

When modal verbs like volere, potere, or dovere are used in compound tenses, they borrow the auxiliary verb of the infinitive that follows them. Because the main verb mostrare (to show) takes avere, the modal verb also takes avere, giving us avremmo voluto mostrare.

Could we use the unstressed pronoun gli before the verb instead of a loro at the end?

You could say gli avremmo voluto mostrare to mean "we would have liked to show them", but you would lose the word "all". Using the standalone (tonic) phrase a tutti loro after the verb allows the speaker to attach the quantifier tutti and emphasize that the action is directed at all of them.