Nuclei with just two protons, also known as helium-2 or diproton, are not stable and do not exist in nature. This is due to the strong repulsive force between protons. The electromagnetic force, which is responsible for the repulsion between like charges, is stronger than the attractive force of the strong nuclear force that holds protons and neutrons together within a nucleus.
In order for a nucleus to be stable, it typically requires an equal or greater number of neutrons than protons. The neutrons help to counteract the repulsive force between protons, adding to the binding force that holds the nucleus together. This is why helium, with two protons and usually two neutrons, is the smallest stable nucleus in nature.
The instability of nuclei with only two protons is a result of the delicate balance between the strong nuclear force and the electromagnetic force. The repulsive force between the protons overwhelms the attractive force, causing the nucleus to be highly unstable and prone to decay.