Read this document if you think your Apple ID has been compromised. --> If you think your Apple ID has been compromised - Apple Support
For iOS 15 or earlier, if you want to see if anyone else has access to your device or accounts, click here --> See who has access to your iPhone or iPad - Apple Support
For iOS 16 or later see how Safety Check on iPhone works to keep you safe. How Safety Check on iPhone works to keep you safe - Apple Support
Related materials:
Personal Safety User Guide
Personal Safety User Guide - Apple Support
> open the Table of Contents and review the articles
A document with general information about security and your Apple ID --> Security and your Apple ID - Apple Support
Contact Apple for help with Apple ID account security by clicking on this link --> Contact Apple for help with Apple ID account security - Apple Support "This article provides country-specific Apple Support contact information for customers seeking help with their Apple ID password or other security-related issues."
If you do decide to instead delete your account, read this support article --> How to delete your Apple ID account - Apple Support
Carefully and thoroughly read this for information about what happens when you delete your Apple ID account. For example:
"Make sure that you sign out of all your devices to avoid issues with apps that use your Apple ID account or iCloud. After your account is deleted, you can't sign out of iCloud or turn off Find My iPhone Activation Lock on your devices. If you forget to sign out, you might not be able to use your device when your account is deleted."
Realize that you will lose the ability to redownload and update everything done with the old account.
This document explains how to create a new Apple ID (create an Apple Account) --> How to create a new Apple ID - Apple Support