In comparison to other stars, our sun is quite average, we can't complain about it, without that we wouldn't be here, but what's the biggest known star in the universe?
The largest star is not the most massive. The most heavy stars are often trivial in terms of their volume, and the largest stars are often just "lightweights." As they age, these objects expand and lose mass.
The most massive and the largest
In terms of mass only, the record is R136a1. You will find this star about 160,000 light-years away from Earth in the Great Magellan Cloud, the Milky Way galaxy-satellite. In diameter, this very young and glowing star is thirty to forty times larger than the Sun, but it is more than 315 times larger.
In terms of volume, the largest of the known stars is probably UY Shield, which is about 9,500 light-years away. The diameter of this red hypergiant is about 1,700 times the diameter of the Sun and is about 192 solar radii.
This error is due to two main factors: to determine the diameter of such an object, astronomers need to know how much light it produces. The further away from us, the less bright it seems to us. Add to this the fact that red hypergiants are often "variable", which means that their brightness is very variable over time. They are regularly glowing and dim.
Other stars are close behind the UY Shield, starting with the WHO G64 and VY Big Dog, about 1,500 times the diameter of the Sun; however, given the degree of uncertainty, they can both be larger than the UY Shield, placed in the center of our system, these stars would cover all the inner planets as well as Jupiter.
The smallest of the famous stars.
On the other side of the spectrum, there are also "bones" stars. So far, the rank of the smallest known star still belongs to EBLM J0555-57Ab. An object whose radius is comparable to that of Saturn is approaching the theoretical limit of the smallest possible stars with a mass of about 0.084 solar masses. In other words, this star is capable of maintaining nuclear synthesis in its core, allowing it to "light" but only a little bit. If it is smaller, it will be considered a brown dwarf.
Of course, we don't know all the stars in the universe. In fact, we can't even measure the size of the stars on the other side of the Milky Way because of the dust, so it's likely that there are even bigger giants in space.