Long-standing decline in violence? What about world wars? Communist mass enslavements and murders? Genocidies which count their victims in millions? I’m no hist

Long-standing decline in violence? What about world wars? Communist mass enslavements and murders? Genocidies which count their victims in millions? I’m no historian so I don’t have the data to do an informed comparison, but the 20th century certainly seems like a horror show to me.