I wonder...
Weaons: North Korea has the third largest army in the world, nukes, and they hate USA.
Cruelty: Burma's human rights violations at the hands of their military, the ruthless Junta, is too much to even describe.
Not much of either: Iraq stated they had no weapons and were no threat to USA. They were promptly taken over, with EASE, and no WMDs were found. One of 2 dozen evil dictators in the world was removed, and replaced. Oh yay. What a good reason.
...Hmm.
If the US had stated that they wanted to remove some random evil dictator, (and stick their nose where it doesn't belong), than the UN never would have allowed the war, and it would have thus been an illegal war... Wait a minute, even with the USA's crappy excuse, it STILL wasn't allowed by the UN.
....Hmm.