Comparison of Regular Adverbs

Remember two simple rules and you’ll have this mastered in no time:

A comparative adverb is always the neuter singular accusative of the corresponding comparative adjective. (ex. clārius)
The superlative adverb is just the superlative stem of the corresponding superlative adjective with –ē. (ex. clārissimē)

Here are some additional examples:

carē, cārius, cārissimē, dearly, more dearly, most dearly
miserē, miserius, miserrimē, wretchedly, more wretchedly, most wretchedly
leviter, levius, levissimmē, lightly, more lightly, most lightly
audācter, audācius, audācissimē, boldly, more boldly, most boldly
bene, melius, optimē, well, better, best
male, peius, pessimē, poorly, worse, worst

The Essential AG: 218