It might be one of his biggest Achilles' heels, but it turns out that Superman actually needs kryptonite more than people realize. Clark even admitted as much to one of his allies on why it's important to have such a lethal threat in Superman's life.
While the Man of Steel is perhaps the most powerful man in the DC Universe, even he isn't without his flaws. For all the powers Clark Kent is afforded under a yellow sun, there are plenty of things just ready to rob him of his amazing powers. Whether its radioactive slivers of Krypton or red sun rays, there's always something that can weaken Superman and give his enemies the opening they need to do him real harm. While there's more than one way to hurt the Last Son of Krypton, nothing is as effective as kryptonite and its many varieties, along with their unique effects.
But despite the threat it poses to Superman, it turns out he's actually okay with kryptonite's presence on Earth (to an extent, at least). In Superman/Batman #49 by Michael Greene and Shane Davis, Superman is reeling from discovering that LexCorp is behind the United States government’s recent batch of kryptonite weapons. It hurts all the more that Clark’s old ally, Lana Lang, was behind the decision to prevent LexCorp from going bankrupt. She identifies the remaining pieces of Kryptonite on Earth, which Superman gets rid of thanks to Batman and Toyman. Superman makes a public display of getting rid of the kryptonite, though he hangs on to one last piece. He gives it to Batman as a preventative measure, and Superman mentions that Bruce had a point that kryptonite makes Clark more human because it makes the threat of death a real possibility for him.
Kryptonite Makes Superman Feel More Human
Comic book fans know Superman is an alien, and they’re also likely aware that he was rocketed to Earth as an infant. As a result, Clark was raised as a human and largely identifies as one. Of course, Superman is still an alien and his overwhelming strength and powers are a constant reminder of that fact. But thanks to a few colorful chunks of meteorite, Clark has a way of experiencing that same fears about his mortality that humanity does.
That isn’t to say Superman’s eager to have a piece of kryptonite near him at all times. But Clark is a godlike being living among humans and his Kryptonian powers, for all the good they do him, also isolate him from the people he cares for. Sure, there are a handful of Kryptonians around, but Clark sees himself as a person of Earth rather than Krypton. As an effective god among mortals, Superman doesn’t often experience the same concerns as they do. But with the threat of kryptonite a potentiality, Clark has something that keeps him aware that his life is finite and can be snuffed out at any point. Kryptonite brings Clark down to a human level, something that Superman truly needs to feel closer to his people.