WW2 had more of a racial element to it than WW1, both in Europe and the Pacific. Presumably you know about the Nazis and their policies, which would ensure that even after surrendering you'd likely have a bad time if you were Jewish or Slavic. The Japanese were similarly brutal, and the Allies were quite nasty to Japanese POWs as well.

WW2 also featured far more civilian losses on both sides - in fact civilian casualties outnumbered those of the military. So, chances are very good that someone you know and love was murdered in an air raid or by firing squad. It is a lot easier to hate the enemy if you feel vengeful towards them, as opposed to seeing them as Just Some Other Fellows that are being thrust into the meatgrinder by politicians.

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That being said, WW2 did have its chivalrous moments, and these particularly happened on the Western Front. There really wasn't any racial animosity between Germans and West Europeans/Americans so surrendering was unlikely to get you murdered. North African campaign is held up as the 'friendliest', and this is likely because neither side's civilians were really involved in the conflict in large numbers so there weren't too many instances of executions or partisan resistance which tends to inflame things. German occupation forces often had a policy of killing 10, 20, 50, or even 100 locals for every German killed by partisans. In many places this could turn minor incidents into major bloodbaths, with cycles of revenge feeding more violence.