Watson and Crick used unpublished x-ray data from Rosalind Franklin and never gave her credit for it. They both were absolute noobs in x-ray structure analysis (I discovered this myself for some time, it IS hard).

Franklin was world-renowned for the quality of her x-rays. One of her coworkers who didn't like her stole the newest data and handed it over to Watson and Crick.

Using other scientists unpublished data without their consent is one of the worst things in science.

Later in his life, Watson said some incredibly stupid and racist things I won't repeat here. He did so several times. It was severe enough for Cold Spring Harbor National Laboratory to dismiss him from all duties and cut all ties with him.