who was called "France's most bitter enemy" in scarlet pimpernel

The Scarlet Pimpernel was "France's most bitter enemy."

From the text;

"Chauvelin, my friend, shall we try to understand one another. It seems that my wits have become rusty by contact with this damp climate. Now, tell me, you are very anxious to discover the identity of the Scarlet Pimpernel, isn't that so?"

"France's most bitter enemy, citoyenne. . .all the more dangerous, as he works in the dark."