A lot of extreme animal activists seem to like the idea of humanity being extinct, but I wouldn't say they would ever put that line of thinking into action. Also seen a lot of Darwinism talk of ppl saying they'd seriously be happy if every "stupid", "ugly", religious, ect, person died off. Though that's just chunks of the species, and not the whole human race. Religious extremist, who rarely follow their actual teachings who want unbelievers to die (but not themselves). As well as terrorists who wish death to another nations, but again not to themselves.
People in power like dictators want others to survive so they can rule over them. They typically just want to kill the the opposition who refuse to fall in line under them. Others just want groups of ppl who they don't like to disappear, but still want to live, and have like minded ppl around.
Even though, personally, I think somethings wrong with you if you honestly wish death on mass groups of ppl (self defense, such as times of war are different, even then you shouldn't aim hate towards the civilian populace). It's probably only the truely mentally disturbed who would wish, or attempt to cause the death of the entire human race (themselves included)
