One of the stronger, more vocal proponents of unlimited atonement was Methodist leader John Wesley.
[1] The namesake of the Calvinist systematic theological viewpoint, John Calvin, seemingly expressed an unlimited atonement position in several passages from his published Commentaries.
[2] The terms unlimited, universal, and general are somewhat of a misnomer and have been adopted primarily to distinguish this doctrine from a Calvinist understanding of limited atonement.
Thus, it is not the same as the doctrine of universal salvation, which holds that all souls will ultimately be reconciled to God, irrespective of faith.
Amyraldism (commonly called "four-point Calvinism" holds to a view of Unlimited atonement that is very similar but not synonymous with the traditional Arminian understanding) teaches that God has provided Christ's atonement for all alike, but seeing that none would believe on their own, he then elects those whom he will bring to faith in Christ, thereby preserving the Calvinist doctrine of the unconditional election of individuals.