ineffective(not having the desired effect; ineffectual) adjective [UK: ˌɪ.nɪ.ˈfek.tɪv] [US: ˌɪ.nə.ˈfek.tɪv]I hope it won't be ineffective. = Spero che non sarà inefficace.
inefficient(not efficient; not producing the effect intended or desired) adjective [UK: ˌɪ.nɪ.ˈfɪʃnt] [US: ˌɪ.nə.ˈfɪ.ʃənt]