You can easily achieve a combo streak of 42 during the combat challenges, which can be started at the arcade machine in Stan's Comic Book Store (marked with a blue book-symbol on your map). Simply keep attacking the last remaining enemy of a round with the Web-Strike attack (RB). The Web-Strike does not actually do any damage, allowing you to keep using the move until you have reached the 42 streak combo to get the "I'm On A Roll!" achievement.