This is a hard question to answer because unlike the IG, 'beating' the UN doesn't require a set level of power or w/e -- it requires a ludicrous insertion of plot-induced-stupidity, and/or character-haxx.
Franklin Richards, for example, might be capable of beating Galactus, but he could not survive the UN. Flip side, Mr. Immortal certainly cannot beat Galactus, but he can survive the UN.