These include stellar flares, where stars suddenly release magnetic energy; and neutron star mergers, where two dense stars collide together.
But one class of explosions outshines the rest: gamma ray bursts are the most energetic explosions seen in the universe.
No gamma ray bursts have been documented in our galaxy yet, which may not be a bad thing.
A gamma ray burst pointed directly at the Earth would probably lead to a mass extinction event, and the end of civilisation as we know it.
Undocumented events may in fact already have caused mass extinction events in Earth's history.