Poll of the Week: Rewind/Erase moments

There come times in each person’s life where you do a facepalm and say in your best Homer Simpson voice: “D’oh!” It is at these times that we wish we had a rewind/erase button. Those moments at the focus of this week’s poll.
With time travel an accepted part of the canon of Star Trek, we do see from time to time the opportunity for the various crews to get a do-over. They missed something, or did something wrong and events went horribly, but they get a chance to make them right. Sometimes the moment’s result wasn’t even all that bad, but it just wasn’t right and the crew finds themselves needing to make it so (no pun intended). The movies have several of these throughout them set, so I have left them out of this poll intentionally
Here’s the ones that jump into my mind! Come share the moments that you think most make the casts want to do face palms!