Superboy, like Superman, derives his Kryptonian powers from the absorption of solar energy from the Earth's yellow sun, and he is as vulnerable to Kryptonite and magic as is the Man of Steel.

Is Superboy-Prime immune to Kryptonite?

While his powers burn out fast, he has some bonuses that Superman does not have. For one thing, Superboy-Prime has immunity to Kryptonite. Just like any human, Kryptonite has no effect on him because his Krypton was swallowed by the sun and there were no remnants spread throughout the universe from an explosion.

Is Superboy weaker than Superman?

Jon Kent has also become the new Superman, but it's just been confirmed in the latest issue that he's actually stronger than the Man of Steel.