The queen Borg in Star Trek: First Contact. Great entrance, just when you think all is lost, Data betrays her, utters the famous line 'resistance is futile', then smashes open the coolant tank. After she's gone, I like Picard picking up her twitching metal skull. Stewart was of course a member of the RSC and it looked for a second like he was about to say 'alas, poor Yorick'...but instead, snaps her spinal chord.
Most bizarre comeuppance:
Brazil: the two annoying plumbers get drowned when the air intake for their hazmat suits is swapped for the sewage outlet, basically filling them up with s**t.
007 movies have loads of villian/henchmen comeuppances, I always enjoy the motorbike assassin with rocket-bomb sidecar in The Spy Who Loved Me...'all those feathers and he still can't fly'
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