Velvet Hammer

Making this due to all the wrong answers posted.
A 'Velvet Hammer' is a MAN who has the ability to beat someone senseless, but acts and dresses like an eloquent gentleman rather than a normal thug.

Somewhat similar to the 'Cultured Thug'

"That gentleman in the Armani suit turned out to be a real Velvet Hammer whenever that big brawl broke out in the club."