Rule 6. When comparing two things, similarity should be there, i.e. similar things should be compared. Examples:
Incorrect – This wall colour is more beautiful than the old one. (wall colour is compared with the wall)
Correct  – This wall colour is more beautiful than that of the old one. (compare wall colour with wall colour)
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. 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.