少(すこ)しも～ないNo es ni (siquiera) un poco (A), (A) no ～ ni un poco

These expressions look similar but have opposite meanings. すくなくない is a double negative meaning 'not a few', which implies 'many' or 'a lot'. For example, そういう人はすくなくない ('There are many people like that.', or literally 'not just a few'.). In contrast, すこしも～ない emphasizes absence. For example, すこしも面白くない ('It's not interesting at all.'), which implies 'not even a little bit'.

ぜんぜん and すこしも～ない both emphasize negation and mean 'not at all.' A key difference is that ぜんぜん, especially in casual speech, can also appear in affirmative phrases, e.g. ぜんぜん大丈夫 ('It's totally fine.'). In contrast, すこしも～ない is more formal and strictly used in negative contexts, e.g. すこしも寒くない ('It's not even a little cold.').

Both あまり～ない and すこしも～ない are used in negative statements, but differ in degree and tone. あまり～ない means 'not very (A)' and is fairly colloquial, e.g. あまり寒くない ('It's not very cold.'). すこしも～ない is more formal and emphatic, e.g. 少しも寒くない ('It's not the least bit cold.').

ことはない and すこしも～ない are both emphatic negatives, but with different nuances. ことはない means 'There's no need to (A).' or 'There are no instances of (A).'. For example, 心配することはない ('There's no need to worry.'), and 彼と話すことはない ('There are no occasions when I talk to him.'). In contrast, すこしも～ない emphasizes absence of degree or amount, e.g., すこしも心配していない ('I'm not even a little bit worried.').

とても～ない is an emphatic negative used to show that something is far beyond one's ability. For example, とてもできない ('I can't do that at all.'). In contrast, すこしも～ない means 'not even a little bit (A)' and isn't limited to ability. For example, すこしも面白くない ('It's not interesting at all.'). Unlike すこしも, とても can be used without ない if the meaning is still negative, e.g. とても無理だ ('It's completely impossible.').

全く～ない and すこしも～ない are emphatic negatives that can both mean 'not at all' or 'not even a little'. For example, 全く飲まない and 少しも飲まない both mean 'I don't drink at all.' or 'I don't drink even a little.'. While often interchangeable, すこしも may sound unnatural when there's no nuance of amount or degree. For example, 全く行ったことがない ('I haven't gone at all.'), which wouldn't fit with すこしも.

なかなか～ない expresses that something is not easily done, often implying difficulty or repeated effort. For example, なかなかうまく話せない ('I just can't speak well.') has the nuance that the speaker is trying but not succeeding. In contrast, すこしも～ない means 'not even a little.' 少しも話せない means 'I can't speak at all.', focusing on the absence of ability without any implication of effort or struggle.

決して〜ない and すこしも～ない are both emphatic negatives, but differ in nuance and formality. 決して〜ない is more formal and mainly used in writing, with the sense of 'by no means' or 'never'. For example, 決して危険ではない ('It is by no means dangerous.'). すこしも～ない is less formal and emphasizes absence of degree or amount, e.g., 少しも危険ではない ('It's not even a little bit dangerous.').