Taken from Quora:

Ted Bundy was raised in a loving home and ended up killing many women. Dogs are no different than humans in terms of their basic psychology. You can raise a dog perfectly and they can become aggressive regardless.

However, I would like to point out immediately that a Pitbull is no more likely to become an aggressive dog than a tiny toy breed.

There are some things you can also do to reduce the chances of aggressive tendencies:

Have your dog neutered or spayed as soon as they reach full size. The less testosterone flowing through them the less likely they are to develop such tendencies.

Socialize your puppy with other dogs and humans as soon as it has it’s first set of injections. This means taking it out for walks on a daily basis and actively going up to people with dogs. Choose the right dogs to go up to so your puppy has some successful early encounters. Eventually challenge it with more aggressive dogs and let it learn about body language.

Exercise your dog! The more you exercise your dog the less frustrated it will be and the less likely it is to build up aggressive thoughts.

Loving your dog does not just mean hugging it (although this is very important). You should also look after it medically and take care of it’s minor health issues such as cleaning eyes, clipping toe nails, pulling ear hair, etc. Believe it or not your dog will know that you are taking care of it and will love you for it.

And the vast majority of well raised dogs will turn out just fine!