As a former Scout main, scout is not designed to run directly at the enemy but to flank them. If you move in and creep up behind an enemy with your scattergun and attack quickly, not even a heavy and medic could survive, which gives the requirement of strategy for Scout mains. It's very easy to underestimate the Scout because of his low health, so don't.
To be fair, there isn't really a "worst" class as they all have advantages and disadvantages in different categories and are all fairly balanced. The better thing to look at is what weapons are the worst, such as the Sandman, Beggar's Bazooka or the Classic.
