GMforPowergamers
Legend
An NPC being intimidating and a PC being Intimidated are very different things. If Krusk the barbarian's natural reaction to being threatened is to lash out, or make his own threats then I don't think it would be fair for a DM to say, you are intimidated.
I would describe the NPC as making his threats and then ask how the PC responds. More power to the Player to have their character act the way they want. (Magical fear notwithstanding)
if Krusk the barbarian's reaction to being intimidated is a fight response, that's fine. I don't see what about that stops him from being intimidated...