Nie vs. niemals?
Any substantial difference at all?

for instance, when would you use niemals instead of nie, and vice versa?

Question

Nie vs. niemals?
Any substantial difference at all?

for instance, when would you use niemals instead of nie, and vice versa?

Answer

Nie and niemals are often used as synonyms. Duden, the bible of German grammar, says that niemals is used instaed of nie when you want to stress or assert your statement. The English translation of these terms points in a similar direction: https://dict.leo.org/englisch-deutsch/niemals
niemals: not at any time, under no circumstances, while these translations do not appear for nie.
But there are some expressions where nie just sounds more idiomatic.
◦er hat sie nie verstanden
◦nie mehr!
◦nie wieder Krieg!

Answer

The words are complete synonyms. The only difference is that "niemals" has an additional syllable, which makes it the preferred choice when you want to emphasize it. But there are also other ways of emphasitzing "nie", such as "nie mehr", "nie wieder" "nie im Leben" etc.