Superman, in a straight fight, is more likely to win against Thanos 13.

Superman possesses superior strength, speed, durability, and agility, making him physically stronger than Thanos 13. Additionally, he has a wide range of abilities, including heat vision, freeze breath, and super senses 3.

However, Thanos's greatest advantage is the Infinity Gauntlet, which grants him the ability to manipulate reality and snap away half the universe's population 13. If Thanos obtains this power, the outcome of the battle could be uncertain 3.

In the end, the outcome depends on the specific circumstances and the strategies employed by both characters.