There were many planetkillers in Legends canon -- even a third Death Star!
The Deathstar III was a "fake" built by the warlord Ennix Devian , but it had a superlaser and a trench with heavier guards than the original Death Star. This is the Death Star that gets destroyed in Star Tours.
If it looks like a duck, quacks like a duck, and can destroy planets like a duck...
Then, of course, there was the Death Star Prototype, which was illogically built at the same time as the production model.
As for the other planet killers in Legends...
The Mass Shadow Generator could destroy all life on a planet, ground all ships in orbit, and destroy the planet itself.
Centerpoint Station could tear planets apart with its hyperspace-driven tractor beam.
Yo'gand's Core was a biomechanical meteor made through Yuuzhan Vong manipulation of moons and an alien species that could manipulate gravitational fields.
A Dark Reaper could siphon out the power of Force sensitives and use it to create a turbolaser blast.
The Sun Crusher could make a star go supernova, destroying all the planets in its system.
The Galaxy Gun was essentially a floating planet destroying gun.
The World Devastators would use tractor beams to tear a planet apart, while keeping its resources usable.
And these are just a select few. The list goes on!