Final answer:
Athanasius dedicated his life to opposing Arianism after his return from exile, reinforcing the early Church's stance on the divinity of Jesus as established by the Nicene Creed.
Step-by-step explanation:
After returning from exile, Athanasius spent the remainder of his life combating the heresy known as Arianism. Athanasius, the Christian patriarch of Alexandria, stood firmly against the theological teachings of Arius, who argued that Jesus, being created by God the Father, could not be divine in the same sense as God. This doctrine quickly spread through various populations, including the Germanic tribes, and was a significant heresy faced by the early Christian church. The First Council of Nicaea in 325 sought to address this controversy, eventually resulting in the Nicene Creed, which contradicted Arian beliefs by affirming the consubstantiality of Jesus with God.
While Athanasius worked in Africa, similar theological disputes were being addressed elsewhere, such as the Donatist controversy, which Augustine of Hippo, another key figure in early Christianity, sought to resolve. However, it is Athanasius who is often credited with laying definitive groundwork in refuting Arianism within the Christian community, preserving a doctrine that underpinned the theological stance of the Church for centuries to come.