I don't think Umberto II was a criminal. However he was not anti-fasist too, he sought to live with them. Unlike Princess Andrew of Greece, he did not saved the Jews there.
Well I don't think that
not saving jews means
not being anti-fascist. Queen Marie-Josè, for istance, didn't save any jew but she
was an anti-fascist.
It's not a matter of
braveness, to me. Greece's situation was far different from Italy's. Greece was under German military occupation, and nazis were everywhere in the country hunting jews; while Italy had been almost free from nazis untill 1943, and so people didn't really know about Italian jews' conditions under racial laws. Moreover, nazis thought Princess Andrew was their supporter as one of her sons-in-law was a member of the Nazi Party, so she was a kind of
above-every-suspect person and she took advantage of that (don't get me wrong, I hold Princess Andrew's actions in high esteem); while Prince Humbert, as he never hid his lack of simpathy for fascist regime (and, above all, for Mussolini) too much, he was a kind of
kept under special surveillance person by OVRA (in short, Mussolini's personal service secret), and he knew that. As a matter of fact, he even tried to start a kind of plot against Mussolini (as Lord Edward Halifax, who knew all that by an Italian high diplomat, repeports in his memories) helped by Grandi and count Ciano (and, possibly, by Marshall Badoglio) but Gestapo found it out and informed Mussolini; however Mussolini couldn't do anything against Crown Prince who wasn't openly compromised, but Ciano, Grandi, Bottai and Senise were all removed from their charges. Humbert was also a well-known anti-nazi (he was also in close relationships with Pope Pius XI, who strongly condamned Hitler's regime with his encyclical letter
Mit brennender Sorge); he detested Hitler and he showed his despise for nazi-regime during Hitler's visit in Rome in 1938, so he was considered "dangerous" by Gestapo too.
You must remember that Humber had been educated to obbedience and respect for superiors since he was a little child, and that it was almost unthinkable to him revolting against his father or the regime; a famous quote of House of Savoy says "
I Savoia regnano uno alla volta" (Savoys reign one at a time). And, above all, Humber was the Crown Prince, and so he couldn't compromise himself too much as he had very many responsabilities and duties before his Country and his People to risk of living them without a future King.