Adding another idea:
The final battle has happened and the Dark Lord's plan is stopped, but at a great price. The leader of the party, a valiant warrior, sacrificed in a battle to distract the villain from the rest of the party while they toppled his plan. Or at least that's what everyone thinks happened.
But the reality is stranger. Unbeknownst to anyone, the Dark Lord almost killed the warrior, but stopped. After all, how can one kill the older brother who cared for them throughout their childhood? So instead, he saves him. After all, his plans have been stopped and everyone thinks the warrior died in the effort, so they don't have to fight anymore. And if the warrior has any complaints? Too bad. He won their fight fair and square.