this is a stupid thread.... but if i had to give an answer it would be the holocaust with out a doubt... the holocaust in ways is still going on today... the effects that it has had on the world is everlasting... the jewish population in the world is still down from where it once was or where it would be if it had never happend... im not downplaying slavery but in 5-10 years of the holocaust there were A LOT more people killed than in 200+ years of slavery... 6-10 milion jews were killed... end of story