How to keep track of candidates who you no longer want to engage with in the future, after deletion

How do other companies keep track of a ‘do not hire’ candidate or someone who failed a recent interview and has requested to have their profile deleted?

Looking for some ideas as we are trying to figure out how to handle these types of situations.

Eg: note on candidate file is ‘do not hire’ and the candidate has requested their profile be deleted.

Eg: someone fails an interview and receives a regret letter, then asks for profile to be deleted that same week.

How are other companies keeping track of things like this? Candidates could create a new profile the next week and re-apply and we’d never catch it unless someone remembered the name and details (unrealistic).