When removing or deleting users, bear in mind that the services in their accounts will no longer be accessible, so you will need to be sure you won't need to access these services again in the future.
This is especially important when it comes to services which have been gathering reporting data as all reporting data which has been gathered for that service will be lost as well and you will no longer be able to generate a report for that service.
In order to avoid this, you can transfer services you're not sure you want to delete over to a different user by following the steps outlined here. This way, these services will be saved and you can the delete them at a later date when you're certain you won't be need them any more.
If the user account you're about to delete has any scheduled posts you'd like to keep, you can export these posts into a CSV file and import them into a different user account in order to post them from there.
You may also want to see what other data you can export from the "Download Data" section (Contacts, Drafts, Queues, e.t.c), and also check our relevant support article here for more information on what data you're able to save from the user account you're about to delete.
Once you've made sure there's nothing else you need from that user account, you can proceed with deleting it by following the steps outlined here: How Can I Deactivate Or Delete A User?