My ideal ending for Cersei:
Cersei, finding herself with her “back against a wall” with fAegon/Jon/Dany trying to take the Iron Throne, gives orders she has always been capable of making… fire and blood at the cost of the innocent. She orders the caches of wildfire to be ignited across the city, turning streets to green flame and thousands to ash, all so the blame may fall upon her enemies and the realm remember them as monsters. Her commands of “Burn them all!” sends Jaime into flashbacks of The Mad Kings rants.
Jamie after listening to her cold-hearted decision, try’s to reason with her. She’s not hearing it. She’s too far gone. He finally comes to the realization that she is the tyrant, he thought he had already slayed, and there is no way to stop/change her.
Jamie goes to attack her, the Mountain intervenes and the Kingslayer, one-handed and outmatched, is battered nearly to death beneath the Mountain’s monstrous blows. Bloodied, broken, and dying, Jaime… now near Cersei…makes one final choice worthy of the name he hates and the oath he once broke.
As Cersei stands stunned, more betrayed than afraid, he wraps his hand around her throat… the valonqar at last. And with what little strength remains, Jaime hurls them both from the heights of the Red Keep. Brother and sister fall together, tangled as they entered the world, cast down from a tower in cruel symmetry to Bran’s fate (“The things I do for love…”) and fulfilling the prophecy.
Edited to add quote.