Our sun is about one million times the size of the Earth. Even solar flares can be massively larger than the Earth, sometimes 30 times the Earth's diameter.
As large as the sun is, it's still tiny compared to many stars. The largest known star is VY Canis Majoris, a red hypergiant star in the Canis Major constellation. VY Canis Majoris is about 5,000 light years away, and it is about ten billion times the size of our sun.
It's believed that VY Canis Majoris only has about 100,000 years left before it explodes. It will be an explosion so huge that it's not called a nova, or a supernova... but a hypernova. It could be so bright that it would be visible on Earth even during the day.