Who was the Akkadian sun god and god of justice?

The Akkadian sun god and god of justice was Shamash.

Shamash was the Akkadian name of the ancient Mesopotamian solar deity known in Sumerian as Utu. Because the sun was believed to see everything that happened during the day, Shamash became closely associated with truth, justice, judgment, and protection for travelers.

His principal cult centers were Sippar and Larsa, where temples called Ebabbar were dedicated to him and his consort Aya, also known as Sherida. Shamash was portrayed with rays emerging from his shoulders and with a saw or serrated knife, probably symbolizing his ability to cut through mountains at dawn or to “cut” judgments.

Shamash appears prominently in the symbolism of Hammurabi’s law code: the king receives authority from the seated sun god. He was also associated with divination and could act as a judge of both humans and gods. The main possible confusion is Utu, but Utu is the Sumerian name for the same deity, while Shamash is the Akkadian form requested by the question.