enemy / foe
Masculine noun. Plural: أَعْدَاءٌ (aʿdāʾ). Can be used for singular and collective. Feminine: عَدُوَّةٌ. Related verb: عَادَى (to be hostile).
The Quran identifies Satan as humanity's greatest enemy and urges believers to treat him as such - through awareness and seeking refuge in God.