Gold Experience Requiem in Vento Aureo. Part 5 is a story about predestiny and being unable to fight fate. The main antagonist's Stand allows himself to avoid any fate because of his Stand, King Crimson. He can see the future and step outside of fate to avoid any harm. GER is a transformation acquired specifically to prevent Diavolo from (sometimes literally) sidestepping fate.
Conversely, Giorno's Stand Gold Experience grants life to anything it touches. Wounds can rejuvenate, trees sprout from the ground, and a parking lot of cars turn into frogs and hop away. When Buccellati is mortally wounded, his soul leaves his body, but Gold Experience's restorative powers allow Bruno's soul to remain inside his corpse. Fate hasn't been defied, as Bruno is literally a dead man walking, but his ultimate fate has been postponed.
Gold Experience Requiem, then. The arrow is a recurring plot device in JJBA starting with Part 4 for its ability to grant Stands, but it really comes into focus with Part 5, especially after Polnareff's Stand takes the arrow into itself and becomes Silver Chariot Requiem. "Requiem Stands" are supercharged by the arrow to obtain an ability that the user needs most in that moment. In Polnareff's case, he wanted to protect the arrow, which manifested as a Stand with the ability to prevent anyone from approaching with the intent of taking the arrow.
Diavolo seemingly acquires the arrow and prepares to use it, but Giorno winds up being the one to hold and stab himself with it, transforming Gold Experience into Gold Experience Requiem, a Stand capable of reinforcing the fate of everyone. It's clumsily explained as "returning to zero", but the long and short of it is that GER prevents causality. Any action fated to occur can be completely negated, including death itself. Being "killed" by GER means the moment before you would actually die, you simply continuously experience the moments before death endlessly, never being allowed to expire.
Also, it looks totally badass.