Question

What is the biggest thing in the universe?

Answer 1

The biggest thing in the universe consists of a galactic filament and a vast group of galaxies bound together by gravity. So, that object is considered as the biggest supercluster known in the universe.

Complete step by step solution:
The Hercules-Corona Borealis Great Wall is the Universe's largest known 'object.' This is a 'galactic filament,' a massive cluster of galaxies bound together by gravity with a diameter of 10 billion light-years! However, this is not a ‘celestial body,' which is a term that usually refers to a tightly bound object such as a star or galaxy.
This object was so big that light takes about 10 billion years to move across this structure. When this structure first came to light the researcher team was looking at brief cosmic phenomena known as gamma-ray bursts.
IC 1101 (with a diameter of four million light-years) is thought to be the largest known elliptical galaxy, and Malin 1 is thought to be the largest known spiral galaxy (with a diameter of 650,000 light-years). Meanwhile, UY Scuti, a red hypergiant star in the constellation of Scutum with a radius of over a billion kilometers – 1,700 times that of the Sun – is thought to be the largest star by radius.
Thus, ‘Hercules Corona Borealis Great Wall’ is the biggest thing in the universe. It was first reported in November 2013 by a team of American and Hungarian astronomers.

Note:
Many of the world's largest particle accelerators are dedicated to gaining a better understanding of hadrons, which are subatomic particles made up of two or more quarks. Quarks are among the universe's tiniest particles, carrying only fractional electric charges.