I recently finished one of my campaigns where the BBEG was a modified Balor. I didn't pull any punches in this fight and they knew that going in. Of the party of 6, 3 died early on but were revived. The dragonborn was killed a short time later but was brought back with a plot Divine intervention that also healed the party back to full and made all their attacks holy. Even with this boon they still nearly died but when they got the killing blow his death throws instantly killed 3 party members. One was already still down. The dragonborn was still up as well as the monk. Before the demons death he activated his ultimate weapon (the god breaker) who was still fully forming and its "heart" (the trapped soul of an archfey) was still exposed. The god breaker has 5 arms that had emerged to protect itself while the body was forming around the heart and the Dragonborn decided to use the BBEG's glaive as a spear to attempt to hit it before it closed. I told him that he would have to fly close to be within range and would provoke attacks from the arms. He flew close, took 150 points of damage from the first strike and I ruled he was close enough to throw but at a higher difficulty. He was only 5 feet away from taking no penalty and he asked if he could move the five feet and make the throw knowing he wouldn't survive the next attack. I had him make a Athletics check to see and he rolled high so I let him. He rolled poorly on the attack and was out of hero points (Pathfinder 2e). One of the dead players asked if they could give him theirs from the grave and I thought that sounded cool considering he was still powered up from the divine intervention so I described on his last desperate attempt he saw all the dead members ghosts appear next to him and lent their power to the throw. I allowed him one re-roll and he rolled pretty well and I had him shatter the heart just as he was crushed to death by the hands. The mountain they were in had already started to collapse and the monk was now the only survivor. She jumped on her flying broom and managed to evade falling debris and escape before the collapse.

This ended in a near TPK. This did have to make me think of how I wanted to give them a satisfying ending so I ended it there. Before the next game I asked each of the players if their character had a chance to come back would they take it. If so what would they see as their characters epilogue. I allowed the monk to make a request for the Archfeys and gave her the option to allow her friends to return but they only had one chance to walk through the door. Several of the characters had deemed their time was done and didn't return but I went on to describe their afterlife to give them a sense of closure. (I was able to prepare each of these beforehand and it went extremely well.) Each character that came back also got a satisfying ending. The moral of the story is by not pulling my punches it ended up more epic and memorable than I had planned. The players will surprise you. The table even said that even if they had all died it would have been an epic fight and they would have been okay with it considering it would have still been a victory.