edit to add the obligatory reference - 'The Ones Who Walk Away From Omelas' - https://www.utilitarianism.com/nu/omelas.pdf
He is also credited as the father of chemical warfare, and directly ran and oversaw development of chlorine and other poison gas weapons for Germany in WWI.
His wife, Clara Immerwahr, committed suicide, using her husband's service revolver, and was found mortally wounded though not yet dead by her 12 year old son An act thought by many to have been a protest to her husband's work.
Parent comment is quite accurate.
I'd just like to add that for an athiest, I am a great believer in redemption.
I don't think that it is time reversible however, that theory was thouroughly tested during the crusades with the system of automatic indulgences and by all accounts it did not go well.
Also, redemption is unfortunately rare enough that you shouldn't cut people much slack over anything genuinely serious, while waiting for them to get around to redeeming themselves.