There are at least five with that name, the first was a power metal band from LA, California the second being a Beatdown Hardcore band from Preston City in the north west of England , and the third one being an alias of DJ Ruthless, a jump-style DJ from the Netherlands, the fourth being a hardcore band from Tokyo, and the fifth being a beatdown hardcore band from Chicago.
1) Ruthless. The name itself describes what the band is all about. Powerful, heavy and aggressive, with no mercy. Read more on Last.fm