I think least favorite part of sewing is tracing the pattern pieces out. But I’m not willing to sacrifice the patterns I’ve paid for and not cut on the smallest lines. Why? Because that one time I did it wrong really infuriated me (and my more-used patterns that I cut out of the pattern tissue are getting a bit beat-up).
My favorite part of sewing is, believe it or not, pressing. I just love taking a seam I just stitched and blasting it four ways with my iron. Whenever I do that, I feel a sense of accomplishment. The seam smooths out and suddenly looks all kinds of crisp and professional.