Competition and Aggression
Using threatening behavior to gain control over something.
Dogs and Aggression
Dogs exhibit aggression due to many reasons, but the main reasons are fear-motivated and genetically predisposed. Genetically predisposed means one or both of their were aggressive for different reasons. Fear-motivated aggression is when the dog feels it's being threatened by one or more things. If they attack you but you did nothing, they were scared by something else. Dogs tend to attack the closest living thing to them instead of the thing that actually scared them, so it could be you or something else, like another dog.
Wolves and Aggression
Wolves tend to fight for rank in their pack. While these confrontations are usually based on psychological abilities rather than size or strength, some of them do end up in fights. The loser of this fight is usually chased away from the pack, but there are rare cases in which the pack chases down this wolf and kills it. The omega, the lowest-ranking member of a pack, usually sees most of the aggression of the pack, and is commonly viewed as more puppy than wolf, even though the omega is usually a full-grown wolf.
Lions and Aggression
One of the main reasons for aggression in lions is for protection of the pride. They use this to defend against hyenas, young male lions, and sometimes other prides. Males usually defend while the females take their young away from the fight. It's usually an easy fight when hyenas and young, abandoned male lions attack, but can be fatal if it's another pride of lions. Females also use aggression to protect their young from predators and other males in the pride, and to hunt for food.