Warning: contains spoilers for Superman: Son of Kal-El #8!
DC's new Superman has a weakness not shared by his more famous father, and it will ultimately destroy him. Jonathan Kent, the son of Clark Kent, has inherited all of his father's super-powers as well as his compassion for all living things, on Earth or otherwise. But in Superman: Son of Kal-El #8, the company reveals Jonathan's debilitating weakness that his father completely lacks: words.
When Clark Kent departed Earth, he left his son Jonathan in charge of the planet's protection - and also gave him his title as Earth's new Superman. Jonathan is much younger than Clark (he even missed his teenaged years as a result of skipping several years) and as such has different wants and needs than his more famous father. Superman's planned secret identity that allowed Jon to live a normal life was revealed in seconds after Clark saved bystanders from a gunman, so he is destined to be Superman forever.
In Superman: Son of Kal-El #8, Superman attempts to divert a large creature away from Metropolis and back to the depths of the ocean. The creature's intent isn't malicious and Superman doesn't want to fight it, but that's not enough to stop the evil President Bendix and the Gamorran guards whom he orders - and can control directly, if need be. This is exactly what happens when Bendix deliberately puts one of the guards in the path of the gargantuan creature, who kills him effortlessly. While Superman is ultimately suceessful at pushing back the monster from the depths, the death of Bendix's Garmorran haunts him.
"You could have put the creature down in a second, long before it was a threat," shouts one of the Gamorran guards as Superman cradle's the dead guard's lifeless body. "This didn't have to happen. You could have stopped this." The guard's words cut deep; even Superman's boyfriend Jay's narration captions reveal that 'Harsh, vile words cut straight through invulnerable skin.' Clark Kent, being more mature, doesn't this issue - but Jonathan is much more susceptible to ridicule and painful insults.
Superman proves the old adage wrong: words can hurt if the recipient believes they are worthy of the insults. Without his friends by his side such as Damian Wayne, Superman is as vulnerable as Clark was to Kryptonite. Perhaps more so, as Superman's weakness is inside his own psyche, and can't be easily dealt with.