Superhuman Strength: He was capable of lifting well in excess of 100 tons;
Superman TRAINS with the weight of the earth, so bitch please...
Superhuman Speed: Gilgamesh could run and move at speeds superior to that of the finest human athlete.
Superhuman Stamina: Gilgamesh's highly advanced musculature generated considerably less fatigue toxins than the musculature of ordinary humans, and most other Eternals for that matter. Gilgamesh could physically exert himself at peak capacity for several days before fatigue began to impair him.
Superhuman Durability: The tissues of Gilgamesh's body were much harder and more resistant to physical injury than those of an ordinary human, and most other Eternals. He could withstand powerful energy blasts, great impact forces, exposure to temperature and pressure extremes, and falls from great heights without injury.
Superhuman Agility: Gilgamesh's agility, balance, and bodily coordination were all enhanced to levels beyond the natural limits of even the finest human athlete.
Superhuman Reflexes: Gilgamesh's reflexes were similarly enhanced and were superior to those of the finest human athlete.
Till now, this only excedes HUman normal capabilities, it's not even close to be match for Superman..
Energy Manipulation and Psionics could help him, though i seriously doubt that is enough to defeat Superman... this is info from the marvel database; i dont know if this varies in a certain comic arc...
- Superman never uses his true force against anyone because he doesnt Kill.