A story that overthrows a king could be one where a noble with a stronger claim to the throne emerges and gains the support of the masses. Or perhaps a story where the king's own immoral actions lead to his downfall at the hands of those he's wronged.
A story of revolution or uprising could potentially overthrow a king. Maybe one where the people are oppressed and unite to fight for their rights and freedom.
Well, a story involving a powerful conspiracy against the king or a heroic quest to expose his tyranny might do the trick. It could also be a tale of a rival kingdom's invasion and successful overthrow of the ruling king.