Rule 7. When the comparative degree is used in the superlative degree sense
Use ‘any other’ when thing/person of the same group is compared.
Degree of comparison example:
Incorrect: Reena is smarter than any student of her class.
Correct: Reena is smarter than any other student of her class.
Use ‘any’ if comparison of things/person is outside the group.
Incorrect: Delhi is cleaner than any other city in Bangladesh.
Correct: Delhi is cleaner than any city in Bangladesh.

Rule 8. When in the same sentence two adjectives in different degrees of comparison are used, both should be complete in themselves.
Incorrect- She is as good if not worse than her sister.
Correct – She is as good as if not worse than her sister.