Utnapishtim

Here we come to the character that can be easily described as a bad guy even antagonist. But first things first. His name is translated as “he who saw life.” Though we would like to interpret it in another way “he who saw death.” Why? This guy witnessed the death of the entire world, which was really awful. In this story, he is former king and priest of Shurrupak, and also he was a very good recipient of Ea’s favor.

Do you remember when Gilgamesh wanted to find eternal life? Well, Utnapishtim always told him that it is a very stupid thing to do, he showed his disdain very visibly. Also, he doesn’t know why among all people in the world Ea chose him to live and see the death of the world. What he knows, is that he and Ea mocked all people in Utnapishtim’s neighborhood to take part in the labor day, where they have to build a boat for him and his family to keep them in safety, but refused to take them with him on the boat. 
So, being instructed before the flood day in Shurrupak Utnapishtim automatically got the role of the immortal person. Gilgamesh seeks him out after Enkidu's death. Also, later Utnapishtim tells Gilgamesh about the flood situations and adds where to find a magic plant which will bring immortality.

This action gave a huge delight to people he knows and to all humankind at all. Also, he gets a promise from all gods that now, all people will be capable to die, and only this will help humankind to continue being and changing. It seems like after these words we don’t see him as an antagonist anymore, though living longer than we do now will be much cooler.