Retard

To delay or hold back in terms of progress, development, or accomplishment.

Example:

When playing video games with close friends it becomes apparent that some are good at the game, others however may act as team retard.

Alternative:
I believe there may have been a misunderstanding when I told my boss I needed some time without interruption or he'd be a retard. (sheesh, you try to get a little space to progress in your work and the guy loses it. Update, it backfired; I am now referred to as the team retard when I have any questions.. still unsure exactly how they mean it -_-)