What is the best acne fighting ingredient if benzoyl peroxide is intolerable or useless ?

Other options: Get with your personal physician now. If topical benzoyl peroxide has failed, you'll probably need prescription-strength rx. Never use an antibiotic as sole therapy; your initial rx might be a salicylic acid wash or topical retinoic acid derivative plus topical Clindamycin or systemic tetracycline. We can manage all acne nowadays but it's not easy. If you're offered isotretinoin, consider it.