The level of aggression that Chihuahuas show towards their owners, strangers, and other Chihuahua dogs is above average. If their pets show threatening behavior towards other people, the dogs are poorly socialized.

It is important to be aware that when your Chihuahua feels threatened or feels you are being distracted, he may act aggressively towards visitors. If you tense up or exhibit negative behavior in the presence of other people, Chihuahuas may understand you and begin to behave aggressively. Your Chihuahuas can get irritated easily if they are depressed or sad, which can also make them angry most of the time. If Chihuahuas get bored or don't get enough exercise to burn off all that energy, they can go crazy with aggression.
They can also become aggressive if you try to brush the fur area with them. Chihuahuas are always alert, aggressive and therefore seem angry. They are aggressive and protective dogs by nature, which sometimes makes them appear tough and angry. Since Chihuahuas are the smallest dogs on the planet, Chihuahuas sometimes manage to misbehave and show aggression.
They're not likely to do much damage, but it's not much fun to have a dog on a rampage. If you have a Chihuahua, then you know that they have a rather large and bold personality. Chihuahuas are small animals and their great attitude may just be to hide their fear. Our Chihuahuas will also be more aggressive when meeting new people or larger dogs than pit bulls.
When properly socialized, Chihuahuas are considered non-aggressive and make excellent companions for families with children; however, due to their strong territorial sense, they can be aggressive towards strangers. Their aggressive behavior can be seen as fun rather than a problem, which causes some Chihuahuas to lack boundaries and trust. Chihuahua owners can have a hard time dealing with this type of aggression at home because the puppy's aggression seems unreasonable.
Small dogs like Chihuahuas or Chivignyes are very aggressive due to their small stature, they are fair and try to protect themselves. Even the smallest dogs, including Chihuahuas, the smallest recognized breed, can be aggressive. In many cases, even successfully retrained Chihuahuas can be more aggressive than some other dog breeds. One might think that such a puppy wouldn't need the same level of training for whatever reason - maybe a puppy is considered unlikely to cause real harm, but a chihuahua that keeps biting could get hurt Or end up being seriously injured. Biting another animal, a child or even an adult.
Keep in mind that while your Chihuahua is often defensive, reactive, and even aggressive, you don't have to put up with it. Aggressive behavior can become part of your Chihuahua's habits if not nipped in the bud and treated properly. If you notice your Chihuahua's aggressive behavior and want to wean it from that behavior, it's important to understand the reason behind it.
Territorial bite prevention starts with teaching the Chihuahua that it is your property and that you will protect it. Otherwise, your Chihuahua will use aggression every time as he will start to think he is an alpha and can get away with growling, clicking, growling and other aggressive moves. By doing this, you are teaching your dog that aggressive behavior can lead to being left alone and deprived of a favorite toy.
If your Chihuahua is showing aggression, leave the room and carry your dog's favorite toy with you for a while. If your Chihuahua reacts violently, stop hugging him and ignore him for a while. If he's aggressive with the toy, you can do the same by taking the toy away and giving it back when he's obedient. To prevent territorial aggression around food, approach your Chihuahua carefully when he eats.
If your Chihuahua behaves aggressively when a stranger knocks on the door, show him it's okay by asking a friend to knock and enter the front door, then reward the Chihuahua with a treat. If you don't like your Chihuahua's behavior, ignore it for a while.
Otherwise, keep them around and expose them to smells and sounds. Let your neighbors know you're just training your Chihuahua and they'll understand. If your Chihuahua is aggressive toward children, your house cat, or other dogs, you can also isolate them from each other and keep your aggressiveness as far away from the cage as possible.
Showing aggression towards other dogs, especially larger dogs, is usually a sign that your puppy is afraid. Aggressive dogs can be very intimidating, as anyone who has encountered an angry bulldog or the like will attest to that. A well-trained dog will be too tired to show aggression, bark unnecessarily, etc. Then take your Chihuahua out for a walk (2-3 times a day) for 15-20 minutes.