FOE
n. countable C1 Advanced US //ˈfoʊ// UK //fˈəʊ// foe
n. an enemy or someone who is against you. It is a more serious and old-fashioned word than 'enemy'.
n. an adversary or opponent in a conflict or contest. Often carries a literary or historical tone, implying a more personal or existential threat than 'enemy'.
The knight faced his foe on the battlefield.
In the final chapter of the novel, the hero must decide whether to forgive his oldest foe or seek revenge.
The treaty was designed to transform a former foe into a strategic ally, though decades of mutual suspicion made the diplomatic transition exceptionally fragile.
Usage
Commonly used in literary, historical, or dramatic contexts; less frequent in everyday conversation than 'enemy'.