A disbeliever, a denier: someone who rejects or disbelieves in God as per Islam (Arabic: الله Allāh) or the tenets of Islam; or more broadly any non-Muslim.
One who holds a false religious belief; a misbeliever.
One not restrained by moral principles; an unscrupulous villain.
One who has behaved badly, or illegally.
Lacking in conscience or moral principles; unscrupulous.
Holding an incorrect religious belief.