Alexey Navalny is Russia’s most prominent opposition figure, an anti-corruption investigator whose exposes have targeted President Vladimir Putin’s inner circle. His sudden illness on a flight from Tomsk to Moscow Aug. 20, which German doctors say was likely caused by poisoning, fits a pattern of what happens to critics of Putin. The Kremlin has been linked to several similar attacks over the last two decades that share another thing in common: nobody is held accountable. Whatever the Russian le