fiercesome, as opposed to fearsome, is singular in meaning. "fearsome" is an oxymoronic word meaning, dually: "causing fear" and "afraid; timid" {Webster's Collegiate Dictionary}. "Fiercesome", invented in 1999, is primarily used as a more efficent word to express great strength or ferocity.
"Did you see that sack in the backfield? That was fiercesome!" "Boxer X knocked out Boxer Y in a fiercesome victory."
by Michael Kleiner November 17, 2004