Any art that is used correctly can be brutal. But there are some that look more "brutal" than others...Some of the ones that aren't necessarily more brutal, but look that way, are; Muay Thai, Silat, Krav Maga, Hapkido, Kaysi, Kali, KAPOP, Shotokan...Among others. But just because they look stronger doesn't mean that they do more damage. I've seen Tai Chi moves that look extremely soft and simple that can break bones.
A martial arts can't be brutal, a punch can't be brutal. It depends on the person using it. Martial arts in its essence is techniques executed correctly. More or less. Brutality is something else.
Any kind of martial art can be 'brutal'.
It depends on how it is being utilized and the energy of the person using it.
For example, you could use Krav Maga for a friendly sparring match or demonstration, or Tai Chi to take down a mugger.
It all depends on the person.
All martial arts is good, brutal, deadly or effective depend on personal user, how hard they had trained, your power, speed, opponent,would make you good fighter.
krav maga is insane
Wondering what the most brutal martial art is?