Marcion of Sinope (ca. 110-160): God of the Hebrew Bible was evil

"Marcion declared that Christianity was distinct from and in opposition to Judaism. He rejected the entire Hebrew Bible, and declared that the God of the Hebrew Bible was a lesser demiurge, who had created the earth, but was (de facto) the source of evil. [...] Marcionites hold maltheistic views of the god of the Hebrew Bible (mockingly known to them as Yaltabaoth), that he was inconsistent, jealous, wrathful and genocidal, and that the material world he created is defective, a place of suffering; the god who made such a world is a bungling or malicious demiurge. "In the god of the [Old Testament] he saw a being whose character was stern justice, and therefore anger, contentiousness and unmercifulness."

A fairly interesting Wikipedia article!