the un is also made out of said nations and if enough of them decide to be richards the un becomes a bargaining chip for the wrong people
Resolutions (In GA, at least) pass based on a simple majority. In the Security Council (the only UN body capable of imposing the economic sanctions that I mentioned), it requires a 2/3 majority most of the time, and US, France, Russia, the UK, and China can veto any resolution.
There haven't been any problems with a majority of countries trying to impose unfair sanctions on another. The bigger problem is the UN not properly placing sanctions on countries that warrant them, or not intervening in conflicts that are clearly genocides (for instance, the war in Darfur).
