I can’t say I’ve had a chicken breed I’ve considered “the worst.” I have had many that couldn’t cut it running the free range gauntlet on my farm, but none that I particularly disliked.
The only breed I got rid of wholesale were my white leghorns. And they were fantastic chickens. Great free range survivors. I simply got tired of white feathers being molted all over the yard.
Going beyond chickens, I’ve come close to swearing off guineafowl. I started with 10, ended up with 5 making it free range long-term, reproduced them to 24 individuals, then they wiped out back to 2 cocks. They have lots of quirks in their natural history that makes them not ideal for my purposes. The hens have a tendency to smell like wet, dirty, horse and nest too far from the farmyard. Predators key in on them within their first night or two of nesting, I think because of their strong odor. The cocks are aggressive to everything else in the farmyard and have a tendency to run off members of their own kind. I’ve had guineas disappear for weeks and show up on trail camera hundreds of yards from the house where they folded into a flock of wild turkeys. There is simply a certain umph in survival that game chickens have the guineas almost have but not quite. Same with domestic heritage turkeys. I don’t respect something that can’t survive and reproduce itself in a free-range farm setting.
Thus I could never be a silkie person.