Healing Magic Is the Hardest

In speculative settings, magic uses range from Utility Magic to world-breaking rituals. Very often, however, it will completely fail at fixing grievous bodily harm (unless some "natural" Healing Factor is in play) or resuscitating a recently deceased person. If healing magic is possible, it will require a disproportionate amount of power to pull off, compared to anything else on the same scale, up to a divine intervention.

This can be justified by Life being a different kind of energy, accessible only by gods, but a simpler (and more realistic) justification lies in the complexity of all living things. Even simply closing a wound is more complicated than just stitching the flesh together, and dealing with organ damage or disease is even worse. In any setting which applies this justification, expect anything as complex as turning someone into a frog to be right out.

Out-of-universe, this is done to make the characters avoid injuries as hard as they would in Real Life. When you can easily recover from grievous bodily harm or be brought back to life altogether, things get a lot less dramatic and the threats, less credible. An alternative approach to increase the risks is to introduce dangers that are either exempt from magical healing or worse than death.

Compare All Deaths Final.

Anime and Manga

 * In the Lyrical Nanoha series, magic can fix cuts, bruises, and even sprained ankles but get yourself wounded for real and it's weeks to months in the hospital.
 * In Naruto they can do a lot of different jutsu's including making 10,000 copies of themselves, summoning giant animals and make themselves almost immortal but Lady Tsunade struggles healing Lee's bones when he gets attacked by Gaara.
 * In Fullmetal Alchemist healing is sign that the alchemist is skilled. In the first anime this is limited to Dr. Marcoh because he has a Philosopher's Stone. In the second anime, there are more characters able to heal, but it's still not something that many are capable of.
 * In Bleach, characters with healing powers are exceedingly rare. Neliel has healing saliva, which only slightly accelerates natural healing—her drooling on Ichigo is played for laughs, but the ability itself is treated as valuable. Orihime has the power to "reject" wounds and injuries on other people, but she can only do it slowly. This power is so sought after that Big Bad Aizen kidnapped her for it. (Sort of.)
 * In Claymore, the eponymous warriors possess an impressive Healing Factor but only two characters (Cynthia and Yuma) can actually accelerate others' regeneration. The fact that there seems to have been no healing techniques used by the many previous generations of Claymores suggests that they were the only ones who actually found a way to use yoki for it. Healing normal humans is right out.
 * In Scrapped Princess, Raquel Casull can blow up buildings just by looking at them funny but all her magic cannot prevent . It takes a personal intervention by Lord Mauser to fix that wound.

Literature

 * The Dragonlance books, based on the early Dungeons and Dragons games, has healing magic reserved to clerics. In the first book of the series, the appearance of clerics with healing powers is a sign that the gods have returned.
 * Magical healing in The Witcher series is extremely difficult even for powerful mages, to the point where trying to treat a critical injury pretty much guarantees the healer dying from overexertion. In the non-canon Revised Ending, Yennefer (who previously brought down fortresses without breaking a sweat) passes out after healing a shallow wound on Ciri's face.
 * In the Arcia Chronicles, Gerika is powerful enough to shake mountains like maracas but gives up on fixing Alexander's hunchback without even trying, saying that only Erasti may be capable of it.
 * Deryni Healing is a rare talent, so rare even before the Ban on Magic that Deryni found to be Healers were actively discouraged from taking vows of celibacy. By the 1120s, only four people in the whole nation of Gwynedd are known to be able to do this, and three of them are blood relatives.
 * In The Dresden Files healing magic seems to be nonexistent, at least for humans (Listens-To-Winds does have some capability in this matter, but he's a Senior Council Member and regularly goes back to medical school). Magic can be used to staunch a wound or keep someone alert, but not in any more direct fashion. Very powerful beings like the Faerie Queens can do more, including fixing a broken spine and . According to the RPG, Summer Magic can be used to heal people (at least, better than most people) as the magic grants some kind of instinctive knowledge of physiology. Miss Gard's Runic Magic and certain forms of Necromancy can also stave off death.
 * In the Iron Druid Chronicles, druid magic is very powerful but it cannot do direct healing on others. Using druid magic to directly harm another living being will kill the caster on the spot and any healing process can harm the patient even if only temporarily. Druids can use healing magic on themselves but to heal other people they need to use indirect means like potions.
 * In The Inheritance Cycle, magic can heal, but it takes a lot of strength - unless it's life-threatening, it's better to just let it heal on its own.
 * In Rivers of London magic can do a lot to the human body, Your Head Asplode, blending people and cats, keeping a severed head alive for decades, but sadly for it cannot heal injuries. A human body is just too complex to put back together again.

Live Action TV

 * Merlin seems to be this way. Merlin has a lot harder time when it comes to healing Arthur the couple of times he does it than he does doing other spells.
 * In Buffy the Vampire Slayer, supposedly they couldn't use magic to fix Joyce because "The Mystical and the Medical do not mix". Given what Willow would later do, this seemed like a cheap cop-out.

Tabletop Games

 * In Dungeons and Dragons, healing spells have traditionally been the prerogative of the clerics, who not so much cast magic as channel the godly powers of the their patron deities.
 * Only in the 3rd and 3.5 editions did Arcane healing spells (i.e. ones that don't require godlike powers) begin to proliferate. Oddly enough, Bards (and anyone with shenanigans to take spells from the bard list) are fully able to heal through arcane spells. The other group who can pull that off are dragons, but they are dragons.
 * Forgotten Realms in AD&D era already had The Simbul's Synostodweomer converting arcane spells into healing magic. Of course, it's high-level, and the developing wizard already was able to do it at will, though with some risk, as a daughter of the goddess of magic.
 * In Ars Magica, you can heal someone easily, but the injury would come back a relatively short while after, and just as bad. Permanent healing required expenditure of vis, i.e. a scarce magical resource.

Video Games

 * Healing magic is available to mages of the Creation school in Dragon Age, but it cannot hold a candle to the Spirit Healers' abilities, which draw upon the energies of powerful benevolent spirits.

Web Comics

 * Psychic healing is possible in Zap, but it takes a very strong telekinetic who has studied anatomy extensively and had a lot of practice.