The most well known antonym for 'immense' is... 'little' !
small, puny, miniscule
Minuscule is the word you seek.
teeny
little
Terror is an antonym for fearlessness.
How about "common"? or "normal"?
what is the antonym of salutation
little
Kind is the antonym of unkind.
hard is the antonym of easy happy is the antonym of sad
Plural
The antonym of flat is round.
Letter
a six sided object
ambient, umbrage, immense, emerged