Supreme Ascendancy is the ultimate power up a Djinn can receive. They receive it only at the end of their lives if its brought about by unnatural causes of murder and they can "survive death" meaning they do literally die but they keep on fighting after they die. This awakens the supreme ascendancy which is worth greater than any zenkai or powerup in the universe and makes them far, far stronger than their greatest most powerful form even though they are still at their weakest and close to death. If the Djinn survives, the door to power beyond gods opens to them.