A progress bar gradient is a visual element used to indicate the progress of a task or process. The 'best-looking' aspect refers to the most visually appealing or attractive gradient design. This can include factors like color choice, blend, and animation. Designers often use gradients to make progress bars more engaging and visually appealing. To achieve the best-looking gradient, one might consider using contrasting colors, smooth transitions, and subtle animations. However, the best design depends on the context and the aesthetic preferences of the audience.