Good stuff gang. First post updated. I think that you may be confused on what Nihilist means though, A3n. It isn't about wanting to control or dominate, but rather being apathetic to life and its meaning/purpose. Thanos is Nihilististic because Lady Death (his only love) rejects him when he dies, so he hates his own life and finds it pointless.
http://en.wikipedia.org/wiki/Nihilism