I've never robbed a bank or murdered anybody, but I've been bad.
If by bad you mean boorish, creepy, or obnoxious you could say I've been bad.
Rapists, killers, and shoplifters probably aren't going to enter this contest. If they are, they're probably not admitting to what they actually did. They'll write about something mischievous or sketchy. Perhaps one of these people will cop to a tryst with a friend's spouse. Perhaps he or she will say the friend in question never suspected anything. Until now.
Somebody who enters this contest probably will do something that is actually bad within a year of pressing send.
There is an excellent chance that somebody writing one of these stories or reading them online will be in jail within the next decade.
If I were to admit to stealing candy bars from a convenience store when I was twelve, you might say I was bad. I could tell you how my heart raced, and that I tried the same thing at another store and was caught by the clerk. How he told my parents and they scared me within an inch of my life. I would be lying. And that would be bad.
Cheating on taxes is bad.
Jumping a subway turnstile is thievery.
Not holding the door, swearing, dining and dashing, not paying your bills, drinking and driving are all very bad. I'm glad I've never done any of those things. At least not that I'm admitting to here.