I was reading some of Marv Wolfman's run for the Brainiac revamp and yeah, Superman absolutely does have a temper. He trashes Vandal Savage's office (at the time Vandal owned a corporation and was basically Post Crisis Lex Luthor) purely out of the frustration that he can't bring Vandal in for his crimes and later he is very blase out his part in blowing up Lexoor; Lex's ideal dream planet which causes Lex to hate him even more ("Hate? No, I've only just begun to know what that means." Chills).