New top story on Hacker News: Ask HN: What is the thing you've build you regret the most?

Ask HN: What is the thing you've build you regret the most?
31 by Octabrain | 17 comments on Hacker News.
Given the very interesting comments on the "Ask HN: What is the most impactful thing you've built?", I was wondering about something similar: Things you regret based on ethical implications, bad technical decisions you made convinced you were right but regret/cringe about later, failures on miscalculations on budgets that provoked a bad outcome in the company etc whatever. Thanks in advance.