A more humane action would be to go back in time and cure Woodrow Wilson of the Spanish Flu. This would have allowed him to neuter French and British calls for blood post-WW1 and leave Germany in better shape, preventing the rise of fascism at all.

America would have continued isolationist but the ideals of the League of Nations would have struck a better chord with Europeans and formed the EU 50 years earlier.

The supranationalist idea of co-operative peace would have given other nations the same idea, having witnessed the alternative at the somme. There would have been no German influence on Japanese aggression and Hitler would have died a penniless artist somewhere in Vienna.