PBW - Loosers Who Quit

[Greybeard]

I'm in a game, as a long-time replacement player, that is no longer fun. I have kept playing, but it's really useless. One player has a much better racial setup than everyone else and is really powerful. He could easily eliminate my empire, but instead chooses to park large fleets on the suns in my systems and let my planets riot.

There are only four empires left, and the combination of the weaker three would not be strong enough to win the fight. I'm ready to declare a winner and leave the game, but the leader seems to want a different type of ending.

What would you do in this case??