largest
adj.adj. bigger than all other things of the same kind. You use this to describe the one thing that has the most size, volume, or amount in a group.
adj. the superlative form of large, indicating the greatest size, extent, or capacity relative to all others in a specific set.
Russia is the largest country in the world.
The company recently opened its largest warehouse to handle the increasing number of online orders.
While several species of whale are impressive in scale, the blue whale remains the largest animal ever known to have existed, surpassing even the most massive dinosaurs in total displacement.
As a superlative adjective, it is almost always preceded by the definite article 'the'.
the most largest buildingthe largest buildingSuperlatives of one-syllable adjectives are formed by adding '-est' — using 'most' as well is a double superlative error.