Two apple ID’s
How do I get rid of one of my apple ID’s
iPhone 12 Pro Max, iOS 14
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Simply don't use the one you don't want.
If you want to be proactive: How to delete your Apple ID account - Apple Support
If you are indirectly asking about merging the accounts, merging Apple accounts (IDs) or transferring data is not officially supported, nor can it be done easily or completely.
Apr. 2018 post by ASC helper Winston Churchill on transferring data from one Apple ID to another. https://discussions.apple.com/message/33333380#message33333380
Feb. 2021 tips from Eric Root https://discussions.apple.com/thread/252468781?answerId=254653802022#254653802022
Look into using Family Sharing to continue to be able to use items purchased with one Apple ID with other Apple IDs.
Family Sharing - https://support.apple.com/HT201060
Set up Family Sharing - https://support.apple.com/HT201088