rope

It's a brush that is already pre-rendered and drawn on a separate layer that has an outline, but because you can't control the line's dynamic thickness and go lower than 1px, it will keep being too dark when it's small xD
The characters mostly have just some cell shading with gradients and drop shadows, so the contrast in rendering makes it even more noticable .
That being said, using the brush/layer combo is super time efficient, fits with the png backgrounds for efficiency