What breed is the most ferocious?

What's best, with respect, would be a good alarm system. Keeping an animal like this, however well trained, is equal to keeping a slightly dodgy loaded gun around. And actually you need a dog who is going to warn, not attack (attack dogs should only be kept in the hands of people who know how to handle them safely). I have to say anybody hearing my Bets, but not seeing them, would have been warned off!! Much as they'd have killed with licking, basically.