This is a weird answer. But it was probably the project that almost ruined my career.

I once started a project to add in A/B testing to a legacy platform that really wasn’t supportive of any such changes. The project was a technical success but a political disaster. The aftermath made it very clear that my manager was hoping I would fail so that he would have an excuse to manage me out. When it didn’t fail he became a lot more obvious in his attempts to get rid of me. I also suspect that some of the issues that happened during the project were setups, but I can’t prove it.

Why am I proud of that clusterfuck? Because it proves that I can still succeed even when powerful people dont want me too. The problems I had at that job were political and not due to a lack of ability on my part. I’m not saying that I am without fault in allowing my relationship with my manager to degrade to tgat point. But I gained a lot of confidence from delivering a working product despite adversity. That confidence led me to a much better job.