Smarter is the comparative; smartest is the superlative.
What's the comparative and superlative of the word "exact"
The comparative is greater and the superlative is greatest.
The comparative is sadder, and the superlative saddest.
The superlative is cloudiest; the comparative is cloudier.
The comparative is "luckier". The superlative is "luckiest".
fewer - comparative & fewest - superlative
The comparative is later, and the superlative is latest
shorter (comparative) shortest (superlative)
Comparative is quieter; superlative is quietest.