The way Olivier looks and acts is pretty intimidating. Same with Buccaneer, but I'd rather deal with him than with Olivier. Alex also looks intimidating, but he really isn't. xD
Orochimaru is intimidating because of the way he looks. the way he acts is no less either, just by talking he can make you poop your pants silly. Madara's arrogant stare also makes him look intimidating, and the casual way he talks about wars and fighting doesn't help. Although Kakashi doesn't look intimidating, when you fight him, it's kinda hard not to be intimidated because the man's a freakin' genius. Jiraiya looks intimidating but he isn't unless angered or when needed to be serious. Tsunade doesn't look that intimidating, but when she's angry, then yeah, scarier than Orochimaru. X_X