Final answer:
The best sentence to introduce the provided paragraph highlighting Gilgamesh's actions and his bravery is 'Gilgamesh proved his bravery when he engaged in battle with a strong and fierce antagonist.'
Step-by-step explanation:
The introductory sentence to a paragraph should set the stage for what is to come and encapsulate the main idea of the paragraph. In this case, it should introduce the concept of Gilgamesh's bravery and the actionable scenario in which it is revealed. The suitable sentence that should be added at the beginning of the provided paragraph to introduce the writer's point is, 'Gilgamesh proved his bravery when he engaged in battle with a strong and fierce antagonist.'