What stops Biden at his old age from doing one last act of vengeance against the people who pushed him out and endorse Trump? He has no legacy that’s even worth mentioning, make the story at least interesting. Post-modern life has corrupted men too much.

Speculative and unfounded; Biden has shown commitment to democracy

Biden’s principles and commitment to democracy stop him, not revenge or corrupted post-modern influences.

I don't think he has the mental capacity for revenge.

he doesn't even know what happened, that will never happen.