Don't need to resize your art for Pixelation. Click on the image, and shift-click on it too. We have a zoom script
It may seem counter intuitive but perhaps what the edge of the sword needs is a darker line and some AA (better AA than what I managed, frankly). That's one way to go. Also check front horn for some pixel-by-pixel alterations to make it work better.
Slightly off-topic, I was wondering about the zoom function here actually ;
I really like it, it's a neat function. What bothers me is that you can't zoom out, and that the pixels get smudged as you zoom in. Is it possible to have the zoom work so that it works like in MS Paint? The smudginess when you zoom in makes it harder to distinguish colours etc.