En superlativo, tienes que mencionar el grupo completo de comparación.

Peter IS the tallest OF THE class 
Einsten IS the most intelligent OF ALL 
The Lamborgini IS the fastest car OF THE Italian cars 
My cousin IS the youngest OF THE family 
Mexico City IS the biggest city OF THE country 
Webster Dictionary IS the best OF THE English dictionaries 
Lilly HAS the longest hair OF ALL my friends 
The Mona Lisa IS the most famous OF ALL paintings in the world 
This cocoa IS the hottest OF ALL in the cafetería 
This IS the shortest man OF ALL the world 

Ojalá te sirva...