致(いた)すTo do (Humble)

The main differences between "いたす" and "なさる" in Japanese lie in their level of politeness and, who they are referring to. "いたす" is a humble expression which one uses when referring to themselves or someone from their 'in group' such as a family member or colleague in order to be humble before others in a formal or respectful setting. On the other hand, "なさる" is an honorific expression used when referring to someone else, especially when they are of higher social status than you, or in formal situations, to express respect or deference.

Both "いたす" and "お〜する" are used in humble speech in Japanese to show respect towards others. However, the main difference lies in their usage. "いたす" is an alternate humble form of the verb "する" and is used when the speaker is referring to their own actions. On the other hand, "お〜する" is a general humble form that can be attached to other verbs to show respect towards the listener's actions. To summarize, "いたす" is used for one's own actions, while "お〜する" is used to humbly refer to someone else's actions.

"いたす" and "する" both mean "to do”, but are used in different contexts. "する" is the standard, neutral term to express the concept of "doing". On the other hand, "いたす" is a humble expression used to show respect to the listener. By using "いたす", the speaker lowers the speaker's own status or plays down the speaker's actions, which is often used when speaking to superiors or customers.