John Piper
Who is this serpent? The fullest answer is given in Revelation 12:9: “The great dragon was thrown down, that ancient serpent, who is called the devil and Satan, the deceiver of the whole world – he was thrown down to the earth, and his angels were thrown down with him.” So the serpent in the garden is the devil (which means slanderer), and Satan (which means accuser), and the deceiver of the whole world. Jesus calls him “the evil one” (Matthew 13:19) and “the ruler of this world” (John 12:31; 14:30; 16:11). The Pharisees call him “;Beelzebul, the prince of demons” (Matthew 12:24). Paul calls him “the god of this age” (2 Corinthians 4:4) and “the prince of the power of the air” (Ephesians 2:2).
John Piper