Clark Kent's already done some silly things to try and get his Kryptonian mojo back, like trying to fly right into the sun. His most recent stab at getting fully powered makes that dumb stunt look like a genius move. For the last six months of DC Comics continuity, the Man of Steel hasn't been able to fly anymore. He doesn't have heat vision or invulnerability either. As you may have guessed, the reduced powerset has made Superman a lot crankier. Readers have gotten strong moments of character development as a result of Kal-El's increased fragility, but he's come across as angrier and more impulsive too. Punching out the Flash, breaking up with Wonder Woman and threatening to disrupt Bruce Wayne's post-resurrection Batman-free life...
... none of those are actions you'd expect from a ultra-compassionate solar messiah. But Clark is more human now and more prone to humanity's missteps.
Extra humanity — in the physiological sense — is exactly the problem that Superman's trying to expunge from his body. See, he's been getting hurt a lot more lately, so much so that Wonder Woman took him to Olympus to get healed by the gods. After surviving a mental gauntlet engineered by Hephaestus, Artemis and Eros...
Superman's wounds were healed. But that recuperation made him completely mortal and he thinks some of those ordinary human cells might be what's stopping him from getting his powers back. In Superman #48 — by Gene Luen Yang, Howard Porter and Adrian Syaf — his crazy plan for getting his powers involves purging those cells with Kryptonite, the element that can kill him.
Now, we already know Superman's going to get his powers back. Still, it's interesting to look at how writer Gene Luen Yang's use of Kryptonite echoes another pivotal moment in Superman history. Kryptonite is sometimes derided in comic book circles, because it's so easy to trot out as a way to challenge or temporarily defeat Superman's nigh-invincibility. At one point, that cliched use of the glowing green rocks got so bad that creators cooked up a storyline in the 1970s that destroyed most of the Kryptonite on Earth. Dubbed the Sandman Saga, these adventures also resulted in a Superman that was also extremely de-powered. He was still much more powerful than the version of Clark Kent fighting evil in current comics, though.
With creators wary of leaning on a rickety old narrative crutch, there've only been a few Kryptonite-centric stories since DC's New 52 reboot four years ago. That makes its appearance in this issue all the more unique: here a frailer-than-ever Superman is using his weakness to try and get back to full strength. He's embracing the possibility of death to become godlike again. It doesn't make a whole lot of story sense but makes for a good metaphor, at least.