Assuming unrestricted leaders what is the worst possible combination of leader and civ? Bonus points if you can find one where they aren't just individually bad but the UU/UB, techs and traits actively work against one another.
There probably aren't that many examples of "UU/UB, techs and traits actively work against one another". The Monument UB civs (Egypt and Ethiopia) are kind of a waste when played by CRE leaders, but Hatshepsut and Zara are CRE and nobody thinks they are bad leaders. There are other antisynergical leaders in the base game -- Alex and Augustus for instance -- and they seem to do just fine. Another way to think of mismatched characteristics is that they give you lots of options; Augustus can kill people with Praets or he can wonder it up.
For the worst unrestricted leaders I'd try to pair bad trait combos with lackluster civs:
Tokugawa, Charlemagne, Genghis Khan, Hammurabi, Churchill (no more Drill IV redcoats)
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Celts, Holy Rome, Japan, America, Greece, Germany [added]
Maybe the worst would be Tokugawa of Celtia? Bad starting techs, traits with no economic benefit, bad UB, situational UU (it starts with Combat 1, but so do Boudicca's; CHA > PRO).