I suppose best means worst because war is bad? Or wars that brought a lot of technological progress?
WW2.
Nukes, air vs navy, Einstein, Indiana Jones, genocide, religious Indian symbols for indoctrination, organized rape and torture, huge ditches for burying rape victims, firebombing cities into dust, eugenics, testing deadly diseases on live humans.
My grandfather was not simply waterboarded... he was hooked up to a water cannon and flooded to near death. Also they would throw around babies, slice them with katanas, then eat them. Even Donald Trump and NPO can't bring back that level of torture.