I actually had an idea somewhat similar to this one.
After the war, Harry and Fleur are an item (idk how, she just didnt get together with Bill). They work as cursebreakers, and a recent expedition had them exploring a necromancer's tomb. to beat his traps and minions, Fleur reads up on necromancy. In climactic battle against an undead basilisk the necromancer had as a final defense, Harry dies while defeating the snake. Fleur panics, and the shattering of their bond by his death sort of.... breaks her. In a fit of desperation, she performs a necromatic ritual on his body. Usually, the ritual results in a mostly living, brain dead creature, who's body doesnt deteriorate as long as it has a consistent magic supply, who also retain their strength from life.
Its Harry. he doesnt do 'usual'. Even after dying. The ritual brings Harry back, as if he had never died, whole, himself. Fleur is ecstatic, Harry is confused, and the world never knows he dies.
They go on with their lives as if the event had never occured, but its not the same. Something's.... missing.
The next expedition, Harry dies again. and Fleur brings him back, with the same results. But its not all good. its about the fifth time he comes back that Harry realises that he's losing himself, his memories, his personality, bit by bit every time he comes back.
He confides this in Fleur, asking her to let him stay dead the next time he dies. But Fleur is having none of it. The shattered bond never truly healed, and Fleur refuses to entertain the idea of a life without her Harry. But their troubles dont stop there. Harry keeps dying, in increasingly gruesome and terrifying ways. There are... things stalking him, trying their hardest to drag him into the grip of death and keep him there. For death doesnt like being cheated of his due.