One heresy in the world today is the belief that Jesus was a man and was not God. In this belief, Jesus was a wonderful person and a spiritual leader. He loved people and taught about God. His life and teachings may have been inspired by God, as the prophets, and some may even believe that he was a special creation of God. This heresy denies that Jesus is God the Son, the second person of the Trinity, and that he is eternal and uncreated. It’s not clear how believers of this heresy explain the many miracles that Jesus performed unless they believe that God simply worked through this human Jesus to bring glory to himself.
This heresy is most similar to Socinianism and its more modern version, Unitarianism. The heresy rejects the Trinity and says there is one God in one person. It claims that Jesus was not divine but was an exalted human. It asserts that Jesus is not eternal and did not exist until he was humanly conceived. This heresy developed during the 16th and 17th centuries and is named after two Italian theologians, Laelius and Faustus Socinus (uncle and nephew). Faustus denied many fundamental Christian beliefs, including original sin, Jesus’s substitutionary atonement, and justification of humanity by the righteousness of Jesus. He didn’t believe Jesus was God by nature. He said that Jesus’s ascension after his resurrection made him and “adopted God.” 1
This heresy is clearly not biblical since the Bible indicates facts to the contrary throughout its pages. As a few examples, the Bible teaches in John 1:1-3; 8:58 that Jesus is eternal and existed with God before Creation and before Abraham. Philippians 2:5-8 says that Jesus is God, is divine and human, and humbly died on the cross to save humanity. Colossians 1:15-17; 2:9 says that Jesus is eternal, came to earth in the flesh, and that God created everything through him.
1Information on Socinianism found here: https://answersingenesis.org/jesus/rise-of-christological-heresy/?srsltid=AfmBOor0JjYakDuEc-IPfEOUQUqZMbEUZK30Zu-cG1f_svOrOHFQMJ1c