Fenbendazole is a pretty good wormer as far as roundworms, capillary, and cecal worms. It won't kill tapes though. Albendazole kills all four and no negative effects have been reported in chickens. People need to follow proper dosage instructions though as with any medication. When in doubt, consult with the manufacturer or an avian vet.
The only annoying part is it must be mixed with feed. Olive oil has to lightly coat the feed before getting the powder to adhere to it for chickens to consume. I like liquids the best. They are easier to administer via syringe. Practicality matters, unless you only have a few hens to dose.