Q: How do i desync purchased albums?

Hi biaancaa,

I'm sorry to hear you are having this issue with iTunes. If your friend accidentally purchased an album under your Apple ID/iTunes Store account and you are now seeing it in iTunes on your Mac, the first thing you would need to do would be to have them remove the account information from their (previously your) iPod. The most complete way to do so would be as outlined in the following article:

What to do before selling or giving away your iPhone, iPad, or iPod touch - Apple Support

Once that has been removed and your friend is using their own account, you should be able to delete the album locally and hide the purchase without any effect on them (though they would obviously need to repurchase it under their own account). You may find these articles helpful as well:

Hide and unhide purchases in iTunes or iBooks on your Mac or PC - Apple Support

iTunes 12 for Mac: Delete songs, playlists, or other items

Delete songs and music videos from your iCloud Music Library - Apple Support

Regards 

No problem, glad to help. So long as your friend stops using your account and switches to their own, any hiding you do shouldn't affect them.

Cheers