Another storyline could be that Thanos, aware of One Punch Man's power, tries to use the Infinity Stones to either eliminate him or make him an ally. There could be a long - drawn - out battle where One Punch Man has to constantly dodge Thanos' attacks while trying to find a way to land his one punch. In the end, he manages to do it and saves the day.
The Saiki K manga ended. It wrapped up the storylines and gave a satisfying conclusion to the readers. Although it's over, it still holds a special place in the hearts of fans.
One interesting storyline could be that Goku, being the ever - eager fighter, challenges Saitama not knowing the true extent of his power. Saitama, on the other hand, is just looking for a normal grocery shopping day. The clash of their personalities, Goku's excitement and Saitama's nonchalance, could lead to a very comical start. Then as the fight progresses, they both start to respect each other's power in different ways.