One of the first gravitational wave detections by LIGO was I think the merger of two black holes or maybe a black hole and a neutron star. It was over a billion light years away I think but was so energetic that it conveted approximately 5 Solar masses into energy in about one second. That's ~10^48 Joules. In 1 second that is ~10^48 Watts.

For comparison, the Milky Way has an estimate of 5x10^36 Watts so we're talking about the energy output, very briefly, of roughly a trillion Milky Way galaxies.

The other that gets me is amgnetars. These are neutron stars with an insane magnetic field. The strongest detected exceeds 1 billion Tesla, making is 30 trillion times stronger than Earth's magnetic field. Get too close and it would flatten atoms and ultimately break molecular bonds and rip electrons out of your body. Google seems to think that happens at ~1000km, which is pretty close to get to a neutron star but still, that's a magnetic field.

These things are quite rare and quite unstable. If you think about it, they must have a lot of protons to generate a field so strong, which means that the gravity is overcoming the strong nuclear force but also the electric repulsion.

> If you think about it, they must have a lot of protons to generate a field so strong

Not necessarily. Neutrons have a magnetic moment. As I understand it, there is a magnetohydrodynamic model of how a magnetar's field gets generated, which would require protons, but it's not the only model and we don't have enough data to be able to rule out other models.