I know I should not, but I do kind of an appreciate a good theologian fracas, when theologians square off. I think this is because the reasons for theologians sparring, unlike most others fights, are at least sometimes (though not always!) substantive. Regardless, the subject matter always matters: who is God and how do we understand Him.
There have been a number of great theologian clashes. One thinks of Athanasius and Arius or Augustine and Pelagius. But another great one was between Tertullian and Marcion. It was not really a squaring off, to be technical about it. Marcion was older. He lived from 85 to 160 AD. Tertullian lived from 155 to 220 AD. So Marcion died when Tertullian was five years old, but that did not stop Tertullian from taking Marcion to task when he got older. In fact, Tertullian wrote a book entitled Adversus Marcionem ,
Why? Well, Marcion developed very problematic views. In fact, Marcion was a heretic. Marcion believed that the God of the Old Testament was a monster, a vengeful, wrathful, false god. He believed that the God of the New Testament was a different deity who revealed Himself in the person of Jesus.