VY Canis Majoris is one of the largest known stars in the Universe in respect of size. The diameter of this red hypergiant is about 1400 times larger than the Sun. Because of its size it is devouring itselve, consuming its fuel at fantastic rates. This star releases as much energy in the amount of seconds as our Sun does in an entire year.
Because red hypergiants are so active, their lifetimes are measured only in millions of years which is a blink of an eye compared to the lifetime of the Sun, which is measured in billions of years. At the end of their lifes they explode in hypernovas; these outbursts contain more energy than 100 supernovae.
Image Credit: NASA/ESA and R. Humphreys
Explanation from: https://www.spacetelescope.org/images/opo0703c/