Avoid using comparative and superlative forms of absolute words such as straight, perfect, round, and unique. Either something is straight, perfect, unique, and so on, or it isn’t. It is illogical to suggest that absolute concepts come in degrees.
Exercises:
Adjectives and adverbs 1
Adjectives and adverbs 2
Adjectives and adverbs 3
Related topics:
Comparatives and superlatives
Form of comparatives and superlatives
Double comparatives and superlatives