~かいもなく/~がいもなく      => despite; even though ~. I tried hard / hard but unfortunately ~ N1
がなくもない => it's not that; I may (double negative) N2
Position, perspective
甲斐がない/甲斐(も)なく => it's not worth one's efforts to do something N2
がないでもない => is not entirely impossible N2
Explain
~べくもない      => cannot possibly be ~. N1
~といえなくもない => It can be said that ~ N1
Concession
くもなんともない => not in the least; nothing like that N3
Base, base
... なくもない => it's not that; I may (double negative) N2
Trend
かいもなく => Even though A, N2
Contrast,Surprise
いくらも…ない => there is only a few/ little… N3
More or less in quantity
~にもなく => ~different from N1
Compare
なくてもいい => Don't have to A N4
Can, Should, Must