Lefty (MR. Enright) is Sally Hardesty Enright's And Franklin Hardesty Enright's uncle 14 years after franks death he arms himself and sets out to find the killer or killers.
In the killer's lair cave he finds franks corpse still in the weelchair with the flashlight in his hand from when he died.
the cook throws a granade from nubbins's sachel and blows up lefty leatherface and the cook while leatherface and lefty are having a duel with chainsaws
In this timeline, he succeed of killing leatherface and thus getting his revenge.
Texas Chainsaw sequels take place in different timelines.