The best example I have for a poorly done progress bars is a drive clone tool I use. It deletes the old partition on a drive, creates a new one than clones the drive. Than does a check to verify integrity. It can do step one and two instantly and says it's half done than takes a bit over a day to do the rest(talking about a couple of TB of data through USB ports here so not that bad and way better than the week it took to do the job with file explorer like they were before I recommended the change