comparison and contrast are different:
I can contrast two statements
John is quite short.
His sister is very tall.
Now put them together with words like: however, whereas, but - and you have a contrast statement.
John's sister is taller than him.
Here's your comparison (in using the adjective + -ER followed by THAN)
There are irregular ones, normally the adjectives with more than 2 syllables.
beautiful - more beautiful