Athens could banish any citizen for a decade by a vote scratched onto broken pottery

Once a year, Athenians could write a name on a piece of broken pottery, an ostrakon, and if enough votes piled up against one person, that person was exiled from the city for ten years, no trial or crime required. The practice, ostracism, was meant to head off any individual becoming too powerful before they could seize control of the democracy.

— Ancient Athenian constitutional practice, Ostracism — in use in Athens from the early 5th century BC