I am not agreeing with GDon. He hasn't even bothered to read the breadth of Marcionite literature and consider what is being said in all of this. Few people have. But if we were to take LSD and think about what Irenaeus is saying about Marcion here's what I think we would come up with.
In other words, Justin and Marcion may have thought that he was Chrestos during the gospel narrative and then after he is "killed" he becomes the Man of War (remember the Psalm cited by Justin) storms the underworld and then was understood to be preparing to destroy the temple.1. Irenaeus was a fucking dogmatist. He was almost mentally ill to the degree with which everyone had to agree on even the minutest points with him. It wasn't like he lived from the time of Jesus and the "apostles" (Marcionite "Apostle"). Yes he gets around this by saying that he saw Polycarp in Asia when he was a boy (! what a fucking stupid argument) and Polycarp saw John and John was allegedly (no he wasn't) the apostle who was the beloved disciple of Jesus. This entire chain of logic is such bullshit we have to wonder how anyone bought into this.
2. Irenaeus as a dogmatist seems to really be attacking Marcion for dividing the godhead. This is often overlooked. His point ISN'T necessarily that Marcion ONLY say Jesus as the Chrestos or "kind power." Rather he objected to Marcion's thinking in terms of two powers PERIOD. In other words, Marcion really follows in the footsteps of Philo and Philo's exegesis of the Bible where Philo says:
a) there are two powers, "Lord" who is the god of bad men and is the power of punishment and "God" who is the merciful god and Jacob started his life attached to "Lord" but at Peniel gave up his allegiance and adopted "God" as his new beloved power.
b) these two powers appear at different times in the Bible to exemplify mercy and judgment.*
3. Marcion almost certainly was just following Philo's system where there were two powers but understood somehow how there was this underlying unity to the whole godhead. In other words, and I don't have proof that Philo believed this, that this one power manifest himself sometimes as "all kindness" and other times as "all judgment." Irenaeus tells us that the Marcionites were evil for "dividing" the godhead. But as sure as tap water can be "all cold" or "all hot" while still always being water, this heavenly power of Chrestos or Christos might have exhibited different characteristics with different advents on the earth.
Marcion and Justin may have believed that water can be "cold" or "hot" in different "advents."
Irenaeus was arguing (even against Justin) that all the powers were one ALL THE TIME.
Look at Irenaeus's understanding of the burning bush. Justin says it is just Jesus in the fire. Irenaeus says it is Jesus and his Father together in the fire. The Marcionites may have just agreed with Justin in so far as the power of God could change from "hot" to "cold" (like my wife) whereas (for philosophical reasons) Irenaeus emphasized a Sabellian like obsession where the full godhead as always present in the manifestation of Jesus wherever he appeared.
* if Philo took a time machine and went to Israel and present his understanding of the Bible he wouldn't be counted as a Jew.