On a scale of necessesary from 1-10.

What is that?

My vote: 0

My brother has two dogs, Filamena and Trooper. They are the same breed (can't recall the breed, they're huge white dogs).

Filly is a sweetheart, you just can't annoy her. Trooper on the other hand is a psychopath. He will bite and growl at ANYONE. He bit my sister-in-law, he growls and snips at me all the time. (He'd bite me but so far I've been quicker than him).

The first time I met him I was spending the night at my brothers house. The dog came into the guest room while I was lying in bed and sat inches from my face growling for 45 minutes. I didn't so much as take a deep breath, for 45 minutes. Finally he left and I jumped up and slammed the door shut behind him.

I've encountered all sorts of dogs. A friend had a coon hound and he warned me off, but I approached that dog with my palm out and the dog rolled over and gave me his belly. My friend was astounded because his dog bit everyone. I've been around snarling shelter dogs which I could tell to "shut up and sit down" and they did.

But Trooper, Trooper is just not right in the head. I could be sitting there all night chatting away and suddenly Trooper will decide I need to be snipped at. He does it to everyone.

My brother has given him doggy Prozac and it has helped. Though he's not still on it. He also got his heirlooms removed and that helped a little. He cannot be trusted though.

Some dogs are just plain mean though.
All creatures can be.
Humans included.

True that, but there is no reason for this dog to be mean. He's well cared for, not abused, has plenty of food and space, has a flock to tend, etc. He has a good life.

My brother has come close to putting him down but I don't think he has the heart to do it.

This is the dog by the way, a Maremma:

And by dog, do you actually mean polar bear?

My aunt had dogs that looked very similar to these. Three to be exact. They were all show dogs. Two were so sweet and docile, and the other turned into a bully. They all were loved, well cared for and treated the exact same way. They had to put the dog away when we came to visit so he wouldn't snip at us kids. But the others were sweet. Weird. And (mumbles) years ago, we would have laughed at doggy prozac. Now...who knows.

This is actually not a new thing. Vets have been prescribing anti-depressant type drugs for animals for years and years. It's very simple, really. Dogs and cats have personalities very similar to ours; they get depressed just like we do, and they can have social issues just like we can. One of my kitties was on an anti-depressant for a little while when she developed anxiety about another kitty in the house. Once she moved past her social issue, we discontinued the drugs.

BTW, those are Great Pyrenees dogs in the pic above.

I've got a Rotti who suffers from separation anxiety- He's totally devoted to my Girlfriend and when she leaves he's completely convinced she's in mortal danger.. We've got him drugged up a little, and he's learning that she returns in one piece..

But Prozac doesn't work and animals aren't going to benefit from a placebo effect.