I let my shopping cart smash into a lady's car at the grocery store. I was unloading groceries into my car and took my hand off the cart for like a second because I needed to use both hands for something particularly heavy, and it was hauling ass across the parking lot when I turned back around. I couldn't catch it in time before it bounced off the side of a car.
I was honest about it though. I sat in my car and waited until the lady came out so I could explain what happened. Luckily. she was nice about it and didn't really care about the little spot it made. Said she would've been pissed if I just drove off, but she appreciated my honesty and wasn't going to worry about it.
It was a total accident, but I guess that's the most recent "bad" thing I've done that I can think of.