Many, more, most.
"Higher" is the comparative of high. The superlative is highest.
Comparative is more and superlative is most.
lazier and laziest
comparative=more superlative=much
'Next' is a superlative; it means 'nearest'. The positive is therefore 'near' and the comparative is 'nearer'.
harmful
last
easier and easiest
The comparative form of rude is ruder, and the superlative form is rudest. It is common to form the comparative and superlative of short words like this by adding -er and -est.
busier, and busiest
stronger and strongest
older, oldest