Few examples are good or bad in and of themselves. What matters more to AdCom is how you position your experience and how you explain its impact on your development. While you certainly want to be honest about a poorly handled situation, you don't need to give every detail about how terribly it may have been handled. Set up the context so the situation is clear in AdCom readers' mind, but then focus more attention on the value you extracted from that experience.
Don't worry about having performed poorly in the past. Occasional missteps are part of the learning experience inherent in life; and as the saying goes, if you haven't failed, you haven't tried hard enough or you aren't pushing yourself. That could be bad, too.