Absolute Superlative is a degree of the adjective where we add the suffixes -ísimo/a, -bilísimo/a, -érrimo/a to indicate a greater quality degree.
Let's look at some examples:
bella bella -->bellísima - extremely beautiful
guapo handsome -->guapérrimo - extremely handsome
amable kind-->amabilísima - extremely kind
In some cases, when adding "ísimo" the prefix of the word changes:
certísimo - extremely certain
novísimo - brand-spanking new
fortísimo - extremely strong
Let's review in sentences:
Está buenísimo. - I'ts extremely good.
Acaba de salir de una enfermedad gravísima.
She just recovered from an extremely serious illness.
La fiesta fue chévere; fue cheverísima.
The party was cool, extremely cool.
The superlative is expressed in two ways.
By the use of adverbs, emphatic prefixes, or both.
muy bueno, muy bien very good, very well
elindo, retelindo very pretty
regrande, retegrande very big
muy rebonito very very pretty
By the addition of the suffix -ísimo, added directly to adjectives or adverbs ending in consonants, and to those ending in vowels after dropping the vowel.
hábil - skillful habilísimo - very skillful
querido - dear queridísimo - very dear
diligente - diligent diligentísimo - very diligent
pronto - soon prontísimo - very soon
Orthographic changes may become necessary to keep the original consonantal sound before adding -ísimo.
rico - riquísimo
largo - larguísimo
When adjectives have ie or ue in the accented syllable, the shift of the accent may revert these to i, o.
bueno - buenísimo or bonísimo
nuevo - nuevísimo or novísimo
viejo - viejísimo
Adverbs with distinctive adverbial endings, such as -os, -a, transfer these endings to the superlative termination.
lejos - far lejísimos - very far
cerca - near cerquísima - very near
Adverbs in -mente have the superlative suffix -ísima added to the original adjective form.
ricamente - richly riquísimamente - very richly
Examples
Rodrigo es el estudiante más inteligente de su clase.
Rodrigo is the most intelligent student in his class.
Rodrigo es el estudiante menos inteligente de su clase.
Rodrigo is the least intelligent student in his class.
It is also common to hear expressions with some of the words implied, though not stated. For example:
Juan es el más alto. - Juan is the tallest.
The suffix -ísimo can be added to the end of adjectives to express an absolute superlative:
El béisbol me parece aburridísimo.
Baseball seems very boring to me.
Estoy cansadísimo, ya no aguanto más.
I'm extremely tired, I can't take anymore.