The word "aggressive" means behaving in a forceful or hostile way, often with the intention of starting conflicts or overpowering others. Full definition
Wii U sales are climbing, and we will be a lot more agressive in a advertising, so you can be sure that we are still in the game, and we will not be going anywhere, for a long time. (nintendotoday.com)
This I found to be Shepherd in March of 2010 and within the first month of having him, he had several instances of agressive behavior toward other dogs. (superdog.com)