Terrible foe (9)
I believe the answer is:
archenemy
(Other definitions for archenemy that I've seen before include "most dangerous opponent" , "Chief foe" , "As Holmes regarded Moriarty" , "Main adversary" , "Principal antagonist" .)
I believe the answer is:
archenemy
(Other definitions for archenemy that I've seen before include "most dangerous opponent" , "Chief foe" , "As Holmes regarded Moriarty" , "Main adversary" , "Principal antagonist" .)