Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
Which one do you use to log into your computer? That's the one whose OneDrive you're using. Visit https://account.microsoft.com/services with the other and cancel your subscription. Then you should be able to visit https://account.microsoft.com/profile and use the "Close account" link there to delete the other account entirely.
I'd caution you to check https://onedrive.com/ for the account you wish to close, just to make sure data you wish to keep isn't there. If you find data there you wish to keep, download it to your computer and upload it to the other account's OneDrive.