I have been through many lenses some were great, some were meh, and some were really bad.
Among the worst I can name zenit 300mm f4.5, heavy, soft, color cast, flares a lot, but I guess it's to be expected, Tamron 28-200 has one of the worst build quality for a lens, it image quality was bad at best, while tokina 24-200 isn't very sharp and flares a little it's quite acceptable and I can say by far better.
Now among modern lenses, the worst one I have used and by far is Sony 16-50, it flares just like the old tamron and tokina, borders are dreadful, non usable without digital correction, however it's tiny and has 16mm so It's here, however compared to Canon 15-85 it is a loser on every single aspect except size and weight, also compared to the kit 18-55 it's also a loser on every single point except it has 16mm.
Among the worst I can name zenit 300mm f4.5, heavy, soft, color cast, flares a lot, but I guess it's to be expected, Tamron 28-200 has one of the worst build quality for a lens, it image quality was bad at best, while tokina 24-200 isn't very sharp and flares a little it's quite acceptable and I can say by far better.
Now among modern lenses, the worst one I have used and by far is Sony 16-50, it flares just like the old tamron and tokina, borders are dreadful, non usable without digital correction, however it's tiny and has 16mm so It's here, however compared to Canon 15-85 it is a loser on every single aspect except size and weight, also compared to the kit 18-55 it's also a loser on every single point except it has 16mm.