Comparison of adverbs in English

The table below shows the way we create comparative and superlative forms of adverbs in English.

Adverb Comparative Superlative
Same form as adjective: fast faster fastest
-ly adverbs of manner easily more easily most easily
briefly more/less briefly most/least briefly
clearly more/less clearly most/least clearly
quickly more/less quickly most/least quickly
Some adverbs of frequency rarely more rarely most rarely
seldom more seldom most seldom
often more often
oftener (less common)
most often
Exceptions: badly worse worst
far farther
late later last
little less least
much more most
well better best

Latest and last can be adjectives.
I have bought the latest CD of Coldplay. (i.e. most recent)
I bought the last CD of Whitney Huston. (i.e. final)

Normally only last is used as an adverb.
That was a difficult question, so I answered it last.
It last snowed six months ago. (= The last time it snowed was ...)

Farther and further can be both used to refer to distance.
He drove then miles farther/further than necessary.