id have to say bubo virginianus is the most aggressive, ferocious species. they arent the largest eagle owl species but they arent afraid of anything (including man, i had a freind who had a pair nest in a huge oak in his front yard and he ended up getting 7 stiches in his scalp after the female dive bombed him on his front porch) they regularly take large animals such as cats, raccoons and opossums as prey and not too long ago a german shepard was attacked by one a couple streets over.