She is the most tallest girl in our entire class.

In the following sentence, a part of the sentence has been bold. Below are given alternatives to the bold part which may improve the sentence.

Choose the correct alternative. Wherever no improvement is needed, choose ‘No replacement required’ as the answer.

The correct answer is the tallest girl.

Explanation:
In English grammar, super-lative adjectives are used to compare three or more people or things to show which has the highest degree of a quality.

For short (one-syllable) adjectives like tall, the superlative form is created by adding the suffix -est (e.g., tallest). Using both most and -est together creates a double superlative (e.g., "most tallest"), which is grammatically redundant and incorrect.

Therefore, "most tallest" should be corrected to the tallest.
Replacing "the most tallest girl" with "the tallest girl" makes the sentence grammatically correct:
"She is the tallest girl in our entire class."