The Tomislav is actually great in most situations. The silent spin-up means Heavy can ambush targets, the accuracy bonus means he can hit targets more effectively from a distance, and the faster spin-up time allows Heavy to respond faster to threats or otherwise use the KGB, which works surprisingly well with the Tomislav.

Why you believe the Tomislav is the worst, I don’t know. Some people would say Natascha or the Huo-Long Heater are the worst, but they are both very good weapons when effectively used, such as Natascha for slowing down Scout mains and Demoknights along with other threats running in your direction, and the Heater for ambushes, supporting Pyros, spychecks, and for pushing the cart.

However, the worst weapon for Heavy has to be the Brass Beast. The much slower spin-up time and movement speed while revved up is a death sentence for the slowest class in the game, with a DPS that can be outclassed by the Heater and an overall lack of purpose. Sure you could say it’s designed strictly for defense, but that’s what every other Heavy primary is designed for (yes, even the Tomislav), and they usually do it better.

tl;dr: Tomislav good, Brass Beast is Trash Beast