Which of these natural disaters at their most devastating would be most destructive?

Earthquakes, megatsunamis and flooding all have the potential to kill up to a million or more people in a single event. However in developed countries (such as the US), earthquakes and flooding will never kill people on that order of magnitude, because of construction standards and advance warning. However, a megatsunami in the right location could cause deaths in the hundreds of thousands even in developed countries, because it could occur with little warning (megatsunamis have local sources) and there could be little time for escape in densely populated coastal areas. For example it is conceivable there could be a megatsunami in the Puget Sound that would leave little chance of escape for people in the Seattle area.