We own 2 chihuahua/rat terrier combos. They are very sweet to me and my wife, but don’t care at all for other people. And they are afraid of nothing at all.
Scrappy, my brother's dog, is 8 lbs of evil. I swear it! I've often told him he should have named him Lucifer instead. My son is no little feller, has lived around pit bulls all of his life, and he is adamant that he will not go into their house unless "the beast" is confined.
This is also one little dog that despises children.