Question

I need the list of all the words whose opposites are obtained by adding a prefix

Answer 1

https://www.englisch-hilfen.de/en/words/opposites_adjectives.htm
Opposites of adjectives in English by adding prefixes - Englisch-Hilfen
you can go through this link for the perfect answer

Answer 2

stable - unstable
variable - invariable
differentiated - undifferentiated
disputed - undisputed
fortunate - unfortunate
impressed - unimpressed
important - unimportant
Hope it helps