Answer is 100% the Leafs.
Just alone of how long ago 1967 was and there were only 4 teams in the division then, but lets look at the fact they have
never won a third round in their entire 106yr existence. Granted - half of that didn't have a 3rd round...but still.
Cleveland Browns have the Cowboys beat by far. They haven't even won the division since the fall of the soviet union.
