Your original question doesn't tell us what tuning process you've done. It is very easy to have this kind of plug simply because the carb hasn't been properly adjusted. If your carb is properly adjusted, and the plug looks like this, there are some other more serious problems in your engine.

Looking at that plug, and I have taken Pe's advice on this learning from him, there's little question it is rich. Follow the best carb procedure for tweaking that you have, fly it some, then take more pictures, if you like.

The fact is the plug tells you the state of overall tuning of the engine; there is hardly anything better to tell you. Tweak it.