Problem with sprite quality

I have a problem with my weapons sprites. They become very ugly on run when they are not vertical. Here’s an example:

This is the configuration of the original picture:

I point out that there is no antialiasing and no anisotropic textures.
Is there something to change in the settings or is the only solution to draw a bigger picture ?

I had a similar error. My problem was that i added a picture with 512px but set the max size to 2048 or even higher. After setting max size to 512 these ugly effects disappeared.

So you should set maxSize as near as possible to the real size of your picture which you use as a sprite.

That could also help: