Heaven Canceller (A Certain Magical Index) can heal anything, whether it is terminal illness or mortal wounds, distorting the laws of heaven, so long as the patient is still alive.
Fiona Fox (Archie Comics' Sonic the Hedgehog) is knowledgeable in medicals.
Doctor (Black Cat) is very skilled in medicals, using soft chi kung to accelerate cellular functions, healing wounds and reattaching limbs.
Retsu Unohana (Bleach) is considered the best healer in Soul Society.
Mayuri Kurotsuchi (Bleach) is very knowledgeable in medical science, having modified many people, including himself, in very innovative, yet disturbing, ways.
Szayelaporro Granz (Bleach) uses his scientific expertise to modify many of his subordinates for extra strength, or transform them into walking medicament.
Tenjirō Kirinji (Bleach) is the most powerful known healer, having taught Unohana many of her medical skills, personally he specializes in balneotherapy, having invented powerful healing hot springs that not only cleanses bodies of impurities...
but also instantly replenished lost blood.
Alfred Pennyworth (DC Comics) is able to perform first aid and more complex medical procedures, thus limiting, if not altogether eliminating, the need for hospital care for the Batman Family.
Hush (DC Comics) is so talented in surgery that he collected certain faces from inmates in Arkham City and stitched them on his to look exactly like Bruce Wayne.
Dr. John Zoidberg (Futurama) was, considered by Professor Farnsworth, to be a fine physician for aliens, despite his knowledge for human physiology was absolutely atrocious.
Tsunade (Naruto) is heralded as the greatest medical ninja in history, able to perform even the most complicated surgeries and even developed the ultimate regeneration technique.
Orochimaru (Naruto) has tremendous knowledge on the human body, having studied so long to achieve immortality and drawing out human strength.
Shizune (Naruto) is Tsunade's first disciple, and has tremendous medical knowledge, even applying them in combat.
Kabuto Yakushi (Naruto) is a very powerful medical ninja, so full of surprising talent that even Tsunade believes him to surpass her prime.
Sakura Haruno (Naruto) has inherited all of Tsunade's medical skills, being her second disciple, and is considered to be her equal in prime.
Obito Uchiha (Naruto) possesses such skill in surgery that he was able to transplant one of Madara's Rinnegan into himself.
Chiyo (Naruto) was considered to be one of the best medical ninjas in Sunagakure, as she created many poisons, and can even transfer life force to bring the dead back to life and heal the injured.
Shinnō (Naruto) may have utter disregard for human life, but his immense knowledge in the human body allows him to perform flawless surgeries with only minor tools, and even enhance his own body.
Tony Tony Chopper's (One Piece) extraordinary medical skills extends to the point he created a drug to enhance his Devil Fruit.
Trafalgar D. Water Law (One Piece) is a genius surgeon, he can treat the most brutal injuries such as magma burnts, and with his Ope Ope no Mi, he can perform miraculous surgeries to treat incurable diseases.
Caesar Clown (One Piece) has medical knowledge, as he could use his chemical expertise to apply healing and turn children into giants, as well as create artificial Devil Fruit ingredients that affect the bloodline.
Doctor Kureha (One Piece) is one of the finest doctors in the world. She could maintain her aging 141 year old body in top physical health and constituion and also trained Chopper into an outstanding medic.
Rebecca Chambers (Resident Evil) is a knowledgeable in medicals.
Asclepius (Valkyrie Crusade)
Minoru Kamiya (Yu Yu Hakusho) has medical knowledge as knowing the by striking certain pressure points/joints.
Stephen Strange (Marvel Cinematics Universe) was one of the world's most renowned neurosurgeons.
Kanzaki Keine (Choujin Koukousei-tachi wa Isekai demo Yoyuu de Ikinuku you desu!) is a medical prodigy and the finest doctor in the world, having successfully saved thousands of patients without a single death.
Dr. Mario (Super Mario) is an excellent physician, having created special Megavitamins that can cure the common cold and the flu.