efficacious
ef-fi-ca-cious
adjective
Producing the desired or intended result; highly effective in achieving an outcome.
"The new treatment proved highly efficacious for the illness."
Thesaurus
Synonyms: impressive, impelling, hard-hitting, effectual, telling, effective, rough-and-ready, trenchant
Antonyms: ineffective, ineffectual, inefficacious, uneffective