Yes, an aggressive dog can be cured. However, it will take time, patience, and consistency on your part. You need to show your dog that you are the alpha leader and that you are in control. This means being firm but calm when disciplining your dog. You should never hesitate or show fear when dealing with an aggressive dog, as this will only aggravate the situation. In addition to proper training, a healthy diet and plenty of exercise can also help reduce aggression in dogs. If you suspect that your dog's aggression is stemming from a medical condition, please consult with your veterinarian as soon as possible.