They are more heavily and most heavily.
While the comparatives heavier and heaviest may be used as adverbs, they do so as forms of the word 'heavy' where it is used (rarely) as an adverb.
Comparative Form- more heavilySuperlative Form- most heavily
The superlative of heavily is "most heavily."
what is the comparative and superlative of glad
The comparative is greater and the superlative is greatest.
comparative straighter and the superlative the straightest
Comparative Form- more heavilySuperlative Form- most heavily
more heavily, most heavily
"More heavily" is a comparative. "Most heavily" would be a superlative.
what is the comparative and superlative of glad
What is the comparative and superlative of Often
The superlative of heavily is "most heavily."
comparative - merrier superlative - merriest
The comparative is greater and the superlative is greatest.
comparative = tenderer superlative = tenderest
comparative: thicker superlative: thickest
comparative - nicer superlative - nicest
comparative - rockier superlative - rockiest