The Holocaust, slavery. There’s no shortage of candidates. Since I have to choose one, it would be the nuclear bomb.
I realize it might have led to consequences regarding the ceasing of hostilities with Japan in WWII, but we’d be better off without the leverage and threat, without the specter of annihilation hanging over our heads every day, not to mention the waste of trillion$ on its development and essentially worldwide procurement.
3 Cents' 