If the goal was to establish themselves as a force to be reckoned with in the comedy world, then Melissa McCarthy and Ben Falcone have delivered a major stumble of a debut with their joint outing Tammy, throwing away any advantage they had from their pairing in Bridesmaids on a clumsily written, tonally awkward script that relied too much on McCarthy’s already overdone shtick and a total lack of empathy for any of their characters.