There are so many truly great villains, it is hard to pick one. However, I don't think Philip Wylie is really a villain! Claire called him a puppy--I think that's what he is. Aside from making a misguided pass at Claire he didn't do them any harm.
The Randalls - Jonathan Wolverton and Frank- caused the most long-term damage to Jamie and Claire. The effects of their actions are still reverberating even now, at the end of 8 books.
Buck on the villains list? I will respectfully disagree with that. What about Ezekiel Richardson? I say Captain Richardson is more a villain than Buck.
BTW - I voted for the Scarlet Pimpernel wannabe.
Actually love reading them all, but St. Germaine is just so disgusting and slimy. Drinking poison couldn’t happen to a nicer person....
Readers, we don't find out until late in the series that arch has pursued relentlessly and intentionally – all totally duped!
Black Jack is almost 100% evil. Bonnet is more complicated. He has mostly selfish motives, but can also be generous.