@Kai, you state, “Jesus spoke of good versus evil but he never spoke of absolute evil (personified by Satan) competing with absolute good.”

Actually there are several references that Jesus spoke of Satan or the Devil:
John 8:44; Mathew 12:26; Mark 3:23; John 17:15; Luke 22:31 and then there is 1 Peter 5:8 and Rev. 12:9-12 and Rev. 20:2.
1 Chronicles 21:1 can be thrown in there for Jesus cited the old testament numerous time and therefore legitimized the old testament as being true.

1. First, regarding Satan: in the Old Testament, Satan at times clearly worked FOR God. He was God’s “bad boy”, who God sent smiting. He was allowed to stand in the presence of God, sometimes rebuked, sometimes not, but what arch enemy gets to hob nob with the object of his hate? When Satan tempted Jesus, Jesus didn’t say, “begone”, He said, “Get behind me.” An odd thing for the son of God to say to God’s “opponent”.

2. Only in the early Medieval period was the Old Testament Satan lumped together with all Pagan deities by church fathers and depicted as the “devil” that we know today. He was given the horns and cloven hoofs of the Pagan god Pan, for example. This was done to demonize non-Christian religions.

3. Jesus spoke of good versus evil but he never spoke of absolute evil (personified by Satan) competing with absolute good. His followers later did, and that “absolute/versus” concept was found in Persian Zoroastrianism, 1,000 years before Christianity even existed.

4. The passage in Isaiah that speaks of the “morning star” does NOT refer to a fallen angel. It’s a reference to an earthly king, Nebuchadnezzar. Only in the 1611 version of the King James Bible do we see, in English, for the first time, the name “Lucifer” used in this passage, a name which, by that time, had become synonymous with “Satan”.

5. “Lucifer” simply means “light bringer”. To the Romans, Lucifer was a minor deity equated with Venus, the morning star. Jesus Himself was once described by Christians with this adjective, and – there was at least one early Christian bishop NAMED “Lucifer”. Clearly, “Satan” and “Lucifer” are one, and eternally evil and in opposition to God, only because over centuries, Christians have made them so.