I have a very "unusual" way to make it less blurry.
You can either make the image in Illustrator or the free Inkscape (vector images) using on pixel sized dot and then scale within the program, export, and upload. This would be somewhat difficult.
Or, what I did, was use GIMP (or Photoshop). Make the image with a 1 pixel brush. It will be very small. So zoom in on the image in GIMP (or Photoshop) and make sure the image fits within the viewable area of your screen.Then print screen (Prnt Scrn button on PCs). Then paste the image back into the image editor. Crop out the unwanted portions and save or export the image, upload, and post.
That how I did mine at least.