What's the Hardest Online Reputation Problem to Solve?

I've been reading a lot about reputation management lately, and it seems like not all reputation issues are created equal.

Some businesses deal with negative reviews. Others face unfavorable news articles, complaint websites, social media controversies, forum discussions, or even outdated information that continues to rank in search results for years.

I'm curious to hear from people who have worked in marketing, PR, SEO, customer experience, or reputation management:

What type of reputation issue is the most difficult to resolve?
Are negative reviews easier to address than negative search results?
How much does the authority of the website matter?
Have you ever encountered a reputation issue that seemed almost impossible to overcome?

Interested in hearing real-world experiences and different perspectives on what makes a reputation challenge particularly difficult.