OK, pick the worst episode in this bunch.

Wolf in the Fold: Scotty's girlfriend ends up killed by a mass-murdering energy being.
The Deadly Years: The Bridge crew gets old real fast (not unlike certain Star Trek shows)
Bread and Circuses: The Enterprise visits the Roman Empire
The Way to Eden: Hippies in Space!!
The Savage Curtain: Abraham Lincoln vs Genghis Khan

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Keeper of the Jabberwock