María es la más inteligente de la clase.
English: Maria is the smartest in the class.
Superlative adjectives in Spanish are used to say that something or someone has the highest or lowest degree of a quality in a group (the most, the least).
Use the superlative to express that someone or something is the most or least (for example, the tallest, the most interesting, the least expensive) in a group or category.
María es la más inteligente de la clase.
English: Maria is the smartest in the class.
Este es el libro más interesante de la biblioteca.
English: This is the most interesting book in the library.
Pedro es el menos rápido del equipo.
English: Pedro is the least fast on the team.
Ellos son los más altos de su familia.
English: They are the tallest in their family.