Recommendation letter from a research supervisor who was not satisfied with my work
Talk with your advisor about this. Depending on your relationship with your advisor, you may still be able to get a decent letter. Use the following formula:


  Decent letter > No letter > Bad letter


If your advisor cannot write you a decent letter you will have to find someone else who is. Do note that not having a letter from your advisor will be a huge red flag; you will have to come to any interview with a ready explanation as to why your advisor did not feel comfortable recommending you.