I know that if an electron collides with its antiparticle, the positron, they annihilate each other and energy is released. But what happens if an electron collides with other antimatter that is not its antiparticle, like an antiproton or an antineutron? Do they annihilate each other too?
Any composite particle can have an antiparticle counterpart if you replace all of its constituent particles with antiparticles (e.g. anti- up and down quarks in the case of protons and neutrons).