There's only one aspect that I truly have a strong opinion about.
Foreign policy. This guy made a joke of the United Nations, this thing we have all built up since WWI. To me, and to pretty much any European people, it's probably the most disgraceful thing I can think about. In other words, George W. Bush Jr. has caused that 3/4 of all the other countries in the UN has gone from respecting the US, to hating it.