Using に対して to express "for," "for the purpose of," or "for verbing"


> 日本語で一番難しいのは、 **一つのことに対して** たくさんの言い方があることです。

Everything I can find on に対して says it means towards, against, regarding, in
contrast to, etc.

In the above example sentence, it seems to mean something like "for the
purpose of," standing in for the "for" in English.

How would you categorize this usage of に対して?

I guess the closest match is "regarding," but that feels like a stretch.

If one of the uses of に対して is "for verbing," how do I know when to use that
instead of something like ために or anything else?

