The UN is basically useless.Think of something "useless" it has done (or not done) then add "security council veto" and google it. ;-)
UN performance depends entirely on the contributions of its member states, particularly those on the Security Council. If the UN is useless, that is because member states make it that way.
"... They ne'er cared for us
yet: suffer us to famish, and their store-houses
crammed with grain; make edicts for usury, to
support usurers; repeal daily any wholesome act
established against the rich, and provide more
piercing statutes daily, to chain up and restrain
the poor. If the wars eat us not up, they will; and
there's all the love they bear us."
-- Shakespeare: Coriolanus, Act 1, scene 1