The vast majority of animals kill just enough to get what they need; food, their own survival, etc. Rarely does a wolf/lion/meerkat/octopus actually kill their rival. The contest is decided when one is obviously going to win and the loser runs off to live another day. Humans also kill for treasure, revenge, slaves, land, power, greed, religion, race hatred, add your own. Humans do not NEED the vast majority of the things we kill each other over, we WANT them, its a vast difference.
What can I say? Millions upon millions have been killed in endless wars that humans have fought, over 3000 since records began. Animals kill to survive, end of. We kill for... Well so many reasons. Usually it comes down to power. We are naturally violent and are masters of death.
I believe humans are the most aggressive animals on the planet, there isn't really anything comparable to us on this planet. I believe we were created to be this way. We had to be aggressive to feed ourselves and you have to be aggressive in today's world to succeed. People who aren't aggressive don't make it very far in the business world.
Yes, humans are more aggressive than other animals, and this can be exemplified by the creation of so many different types of weapons that are designed to hurt both animals and humans. Animals also show aggression when competing to survive, and humans can show acts of aggression that cannot be explained.
Humans are no more aggressive than many animals. Humans likely would be more agressive, but human ingenuity has allowed us to evolve to the point where life-giving essentials like food and water are able to be produced and stored in abundance, dramatically reducing violent competition for those resources that occurs in nature.
No, humans are not more aggressive than other animals, because all animals have the capacity to kill. This is true of humans as well. We kill to eat and we kill because of passion. This is no different than the entire rest of the animal kingdom. We are just one type of mammal.