The Gibbard-Satterthwaite theorem proves that every non-dictatorial voting method is manipulable.
Voting Method
Scenario
Gibbard-Satterthwaite Theorem: Any voting system that uses ranked ballots, has 3+ candidates,
and is not a dictatorship can be strategically manipulated. Some voters can get a better outcome by
lying about their preferences. This is not a flaw in specific systems -- it is a mathematical inevitability.