“Ruthless” (**1/2 out of four) was a gritty suspense melodrama about a high-school wrestling teacher (Dermot Mulroney) whose daughter is viciously murdered; when he finds out that one of his students (Melissa Diaz) is kidnapped by sex-traffickers (led by Jeff Fahey), he takes matters into his own hands and goes after those responsible one lowlife at a time. Mulroney’s strong (and believable) performance is film’s main source of strength helping viewers to overlook film’s shortcomings and familiarity. Similar to 2013’s “Prisoners” and not at that film’s level but still potent and involving.