Relative Superlative indicate the greatest or least quality degree of one or more people in relation to others in a specific group. We use the most, best, least, or worst of all with the formula: el/la/los/las + noun + más + adjective.

El tren más rápido.
The fastest train.

To express the least of all, or worst of all, we can use the formula: el/la/los/las + noun + menos + adjective

Rodrigo es el estudiante menos inteligente de su clase.
Rodrigo is the least intelligent student in his class.

Sentences may have a different construction and still covey the same meaning:

Samuel es el más inteligente.
Samuel is the most intelligent.
Juan es el más alto.
Juan is the tallest.
El barco que es menos peligroso.
The ship that is the least dangerous.
(The least dangerous ship.)
El marinero más delgado es José.
The thinnest sailor is José.
Mi amiga es la más guapa de todas.
My friend is the prettiest of all.
Es el profesor más amable de la escuela.
He is the nicest teacher in the school.
¿Quién es el más guapo de la escuela?
Who is the most handsome of the school?

Note! The superlative always uses de to mean in or of. (e.g. the largest in the world, the smartest of the students)

Chile es el rival más fuerte de España.
Chile is the strongest rival of Spain.

Grecia es el país más débil de la Unión Europea.
Greece is the weakest country of the European Union.

Video - Use of Superlative Adjectives

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