5. You'll need to get your primal.net/dude link back from Primal (example) to ensure that if your profile has been linked to on the web by others then it'll go to your new npub. (Many people are going to share your profile via a link) To do that you'll have to prove you are you to Primal, but Primal might be hesitant, as that'll make them look like a central authority. And that's assuming you have a way to prove to them that it's "your link". There are a few clients that make such links.
6. You'll have to accept that all the places on the web that have shared you via pasting your npub directly (StackerNews, Reddit, whatever), or where you've shared it yourself, are at best dead links, and at worst (if you can't nuke your account) leading unsuspecting people to a phishing account.
7. All your private DMs are potentially exposed
8. If you're slow to nuke your account the hacker can insert notes in the past from before you announced you lost the key, causing much confusion