Not To Be Confused With
The atonement (THAT Christ's death saves) is confessed by all Christians; the theories of atonement (HOW it works — penal substitution, Christus Victor, etc.) are emphases, not mutually exclusive heresies.
A rare English-coined theological word — “at-one-ment.” Scripture piles up images: sacrifice, propitiation, redemption, victory, reconciliation, ransom. The major theories each seize a biblical thread; most traditions hold several together with one in the lead.