How aggressive are Akitas?

I've heard that Akitas can be quite fierce and protective of their families, but I'm curious about the extent of their aggression. Are they known to be overly aggressive or do they only display aggression when provoked or threatened? What measures can owners take to ensure that their Akitas remain calm and well-behaved, especially around strangers and other animals? Additionally, are there any specific breeds or lines of Akitas that are known to be more aggressive than others?