There isn't an "aggressive" breed, an animals behavior depends on how it was raised and their individual personality.
Aggressiveness can also be heritable. But "aggressiveness" could be too-strong of a word. Flighty, nervous, wild, etc. are words that could describe animals that are not aggressive but very unsure and nervous of human presence. Breeds like Limousin, Charolais, Maine Anjou, Black Angus and Salers all have selections for such genetic traits as docility.
However, aggressiveness does have implications as to not only how the animal is raised, but how it is (or was) handled, the environment it was raised in (out on the range where it only sees humans once or twice a year, or on a farm where it gets exposed to human contact at least twice a day), and even individual characteristics. A bull that has been handled a lot and seem very docile can suddenly turn into a mean killing machine in an instant, sometimes for no apparent reason. Even a cow can do the same. Often times the warning signs are there but so suttle that someone who has been around these animals for a long time doesn't see them.
So really, there is no aggressive breed, but there are breeds that are less docile than others, like those listed above.
There really isn't an aggressive BREED per say, as it depends on each individual animal within a breed, since there is more variations within a breed than between breeds. I mean, you can have an aggressive Hereford where most of the cattle in this breed are quite docile. However, the Spanish Fighting cattle are considered the most aggressive breed since these animals are bred to fight with the matadors in the spanish bull fighting ring. In my opinion, Salers are pretty ornery too, but not nearly as ornery as those Spanish Fighting cattle.
The Angus breed.
in my opinion the Aseel is the most vicous
Belgian Blue cattle.
ANGUS of course!!
The Brahman breed is the most heat tolerant, originating from India.
The Hereford breed.
Steer are not aggressive animals. Steer are male cattle who used to be bulls, but were castrated at some point in their life, most likely early on while it was young. This is to prevent the animal to breed with any cows or heffers in the field, and to also make them unaggressive.
Jersey
Angus cattle are the most common.
Angus.
Milking Shorthorn's.
It would have to be the Holstein.