There are various synonyms for the word "fennier," which means more sneaky or crafty. Some possible options include sly, cunning, wily, devious, tricky, shrewd, scheming, conniving, artful, and foxy. Each of these terms can be used to describe someone who is highly skilled at manipulating situations or people to their advantage. Whether used in a positive or negative sense, these words convey a sense of intelligence and strategic thinking that allows a person to achieve their aims while avoiding detection or consequences. Overall, there are many nuanced variations in meaning among these synonyms, but they all share a core sense of cleverness and astuteness that marks a "fennier" individual.