Yes, it's possible for ranch dressing to kill a dog. The reason is that ranch dressing is high in fat and salt, both of which can be harmful to dogs. If a dog eats too much ranch dressing, it can lead to pancreatitis, which is a serious condition that can be fatal. Dogs also shouldn't eat too much salt, as it can cause them to develop sodium ion poisoning, which can also be fatal. So if you're concerned about your dog's health, it's best to avoid giving them ranch dressing.