Adverbs can have superlative forms to show extreme difference in the way things happen.

 

Which animal runs the most quickly?

 

Caterpillars move the slowest.

 

Dave visits doctors the least frequently.

 

To make superlative forms of most adverbs, use: 

‘most’ or ‘least’ + adverb:

 

Of all aircrafts autogyro flies the most safely.

 

You should consider my proposal the  most seriously.

 

Bob is lazy, he cleans his flat the least frequently.

 

This music sounds the least harmoniously.

 

Adverbs ‘well’ and ‘badly’ have the same irregular superlative forms as the adjectives ‘good’ and ‘bad’:

 

good → well → Stephanie plays violin the best in her group.

 

bad → badly → Ben knows multiplication table the worst.

 

Some short adverbs, like ‘early’, ‘fast’, ‘slow’, ‘hard’, ‘high’, ‘long’, have superlative forms of adjectives with ‘-est’ at the end:

 

Your walk the slowest I can imagine, let’s hurry up!

 

This aircraft can fly the highest in its class.

 

I can run this distance the fastest in my age group.

 

Of all his colleagues Phil works the hardest, and his boss appreciates that.