We use comparatives to COMPARE two or more things that share the same quality.
When one of them has more ( of a quality) than the other we use the COMPARATIVE: The formation of the comparative and superlative depends on the number of syllables in the adjective.
This is a nice dog. This dog is nicer than my brother's
When both things, people and places share the same quality we use AS ...AS or NOT SO ... AS
It is AS hot AS yesterday.
You are AS charming AS your brother.
He is not SO cheerful AS his father.
This chair is not SO comfortable AS that sofa.
The peacock is the most beautiful.
The peacock is the most active.
The peacock is the most charming.
The peacock is the most cheerful.
What is her father like?