foe has 3 distinct synonyms spread across 2 of its 2 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. Its one recorded opposite is friend.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
an armed adversary (especially a member of an opposing military force)
“a soldier must be prepared to kill his enemies”
a personal enemy
“they had been political foes for years”
Synonyms, antonyms and the broader and narrower relations for foe come from Princeton University’s WordNet. Full sources and licences.