Death-Activated Superpower

Winning the Superpower Lottery is a good thing, right? Well, unless you're Blessed with Suck or Cursed with Awesome. But, what happens when you're a Differently-Powered Individual whose powers only activate upon your death? Kind of a downer, huh? Well, depending on whether permanent death is in your setting, or not so permanent, it can range from bad to downright awful. Fortunately (for the persons possessing these powers), permanent death is a minority regarding this trope. But if it is permanent, it obviously won't be a useful power during their lifetime, so the real question is: what does it mean for the rest of the world?

Compare My Death Is Just the Beginning and Thanatos Gambit. Super-Trope to Auto Revive.

When used offensively, this is an example of Taking You with Me.

As a Death Trope, Spoilers ahead may be unmarked. Beware.

Examples of Death-Activated Superpower include:

Anime and Manga

In One Piece, Brook's power only activates when he dies. It's the power to come back to life once. Considering the setting, this would normally make him a normal human with Super Drowning Skills. However, when he died the first time, a string of coincidences left him reanimating as a living skeleton, with enhanced longevity, speed, and other related skills.
In the first filler arc of Bleach the Bount Yoshino is the only one of her kind that can create offspring. If she dies, a bunch of life-harvesting Bitto insects can be created. Filler Villain Kariya kills her, his former love, for just that, in order to make his comrades more powerful.
- In his third fight with Ulquiorra Cifer, having about 75% of his chest ERASED by a point-blank Cero Oscuras from Segunda Etapa Ulquiorra resulted in not only an Auto Revive by Ichigo's inner hollow but also making him a mindless God of Warfare that Ulquiorra couldn't even scratch until after the fight was already done.
Scrapped Princess: You remember how they've been trying to kill Pacifica to stop her from becoming "the Poison That Destroys The World"? Turns out the power automatically activates when she dies several hours before it was meant to activate naturally; it isn't clear whether she would have had to die to activate the powers under other circumstances or not.
There are many fans of Code Geass who believe that some of the powers in that show work this way, although the show leaves it open to interpretation. In particular, many of the traits that come with being a Code bearer, such as losing one's Geass, immunity to Geass, not aging, and having weird mental connections with certain people, are thought to not activate until the first time someone "dies" after receiving their Code (which makes them immortal).

Comic Books

In Watchmen, the "Squid" sent nightmarish images of an alien invasion into the minds of survivors after its death by explosion.
The aforementioned Resurrection Man from DC Comics has the ability to come back to life with a new power when he's killed.
Earlier than Resurrection Man, The DC Universe had Immortal Man whose power to was reincarnate in a new body every time he died.
The Phoenix Force from X-Men is supposed to work this way: it activates when the wielder dies (or is about to die) and imbues them with abilities they never possessed before. You must be a compatible psychic host for the entity to possess you, however. To date, Jean Grey has been the favorite choice unfortunately for her....
Norman Osborn aka the Green Goblin discovered his Healing Factor after he was fatally wounded by his own glider in the battle against Spider-Man in the "Death of Gwen Stacy" storyline.
Deadpool attempted to defeat cancer with a Healing Factor that didn't seem to work - until a fatal injury forced it to work at full power.
The original introduction of Wildfire as Erg-1 in the Legion of Super-Heroes showed him as having such a power; as an Energy Being in a suit he could explode, but that would kill him. It was later revealed that he stayed alive as a disembodied energy that was eventually able to reanimate his suit.
Doomsday from Superman was engineered to come back from death stronger, each time improved to resist whatever killed him last time. And then dropped onto a Death World by its creator. What could possibly go wrong?
Marvel's Great Lakes Avengers had Mr. Immortal, whose only superpower was the ability to come back from the dead.
In All Fall Down, AIQ Squared learns the hard way that Siphon has this.

Fan Fiction

In 'Nexus' For Jack to have finished his transformation into a half-demon, he had to die first.
There are several Death Note fics where Light becomes a Shinigami. Like the fic The Prince of Death or the Doujinshi "God's Eye."

Film

Jedi “Force Ghosts” in Star Wars.
In The Matrix, the shock of dying in the Matrix is the last stimulus required to awaken Neo's powers.
- The trope technically also applies to Agent Smith as well, as Smith's "deletion" at the hands of Neo shortly after his powers as The One awakened was what resulted in his ability to duplicate himself and take over Redpills and Bluepills alike.
Seems to be how Selina becomes Catwoman in Batman Returns.
This is how the immortality of Highlander characters is triggered in both the movies and series. And it must be a violent death. A bit of an inversion, however, at the person who dies has to give up said power to the highlander who kills him, rather than received it upon being killed.

Literature

In The Dresden Files, wizards can cast a "death curse", which is essentially a powerful Cast from Hit Points curse, on whoever killed them. Of course, the invention of means of killing from extreme long range make it much less of a barrier for normal humans to kill them...
In The Hollows, when a human is first infected with the vampire virus, they gain some benefit but remain alive. Only once they die from some other cause do they become full-on undead and gain the full suite of powers (and the transformation isn't guaranteed unless the virus was passed down from a parent).
The Draconians from Dragonlance. If you're lucky, they turn to stone or into a (dead) clone of yourself. Bad things include point-blank explosions, melting in a pool of acid, and a repeated, magical blast.
In the Ancient Future trilogy by Traci Harding, immortality is genetic, but the gene must be "activated" by death or other means to be able to pass it on.

Live-Action TV

In Misfits, Nathan's Healing Factor only works on wounds that kill him.
Jack Harkness in Doctor Who and Torchwood is a fact of the universe, and hence it will never allow him to permanently die. As a result, he is immediately resurrected to the same state he was before his first death (more or less perfect health), with all physical and mental traumas healed.

Tabletop Games

Warhammer 40,000: One of the Space Wolves characters has a stasis bomb in place of a second heart. When he dies, the bomb activates and all models in base contact are removed from the game. Including Titans. All affected are locked in a time loop, and forced to listen to his last laugh. Forever.
D&D has a spell called Contingency, that can do this if you know another spell that would be helpful. Though, the condition for activating the second spell can be just about anything—it doesn't have to be your death. On the other hand, the spell gets triggered when the specified condition occurs, whether you want it to go off at that moment or not.
- There are a number of Epic Destinies who have powers that state: "once per day when you die" as their activation condition. Usually, it involves getting revived.
There are several Magic: The Gathering cards which have abilities which activate on conditions which would normally cost you the game.
- Storyline-wise, Planeswalkers (primarily Pre-Mending) sometimes had their sparks activated at the point of death. Examples include Urza after the detonation of the Golgothian Sylex, and Sorin Markov after vampirization by his uncle.

Video Games

In Doom, the Pain Elemental can spawn a number of Lost Souls when it dies.
Various monsters in Diablo II have devastating "cast upon death" abilities. The player characters can acquire some of those, too, a great aid in retrieving your own body.
Albert Wesker from Resident Evil gains his powers after his death due to a virus he injected himself with.
Phoenix in Marvel vs. Capcom 3. If she dies with five super meters stocked, she resurrects as her Super-Powered Evil Side, Dark Phoenix.
In Final Fantasy VII there is the Final Attack Materia, which lets you cast the spell/effect of any materia it is linked to... Including The Life Spell or Phoenix Summon, meaning that as long as you have enough MP, you simply will not die (and with the correct materia combination to draw MP from anything, you are basically immortal).
- The Final Attack materia is limited to five "uses" per battle when fully leveled up, however. Using the combination twice on the same character might work, or it might make him cast the spell twice when dying instead.
One Cyberware implant available in Shadowrun is a tactical nuclear device implanted in the skull. It can be detonated by remote or, of course, dying.
There is an altar to a god in Arcanum, that grants you a great power if you bring an offering to it. The catch is, you need to sacrifice yourself. If you do it correctly, you are resurrected.
Pokémon has the move Destiny Bond, which, when used, causes the Pokemon who K.O's the user to be instantly K.O'ed if Destiny Bond was the last move used by the user. It directly ties in with the "death" (or in this case, "knockout") of the user - if the user isn't knocked out, the move is completely harmless. This can be extremely useful in competitive play, as it allows a badly injured Mon nearing the end of its usefulness to quickly and efficiently take down a key opponent.
- There is also the Mana equivalent in Grudge; If the user of this move is K.O'd immediately after its use, the move that the attacker used for the K.O loses all its PP.
In [[WoW]], the priest class has a talent technically called Spirit of Redemption, but usually referred to as Improved Death. When the priest is killed, they temporarily become a spirit healer which allows casting of all healing spells at no mana cost.

Web Comics

Sluggy Freelance mentions that this sort of power is hard to predict; even Hereti-Corp scientists don't consider their test subjects expendable enough to test for this.

Web Original

Professor Ozpin of RWBY reveals in episode 3 of Volume 5 that whenever he dies, he reincarnates into an existing young adult male, and the two eventually merge into a single being.

Western Animation

In the South Park episode "Fantastic Easter Special" (a parody of The Da Vinci Code), Jesus' superpowers only activate when he is dead, so Kyle has to kill him for him to save the day.