European Stag Beetle

Hi ArisL, Your European Stag Beetle is a female. You can see pictures of the male and female in Wikipedia. Please note that although the Wikipedia article does not specifically mention Greece in its Distribution section, Greece is included on the distribution map. So, you should be secure if you call your spotting Lucanus cervus. There are also many pictures in inaturalist which you might want to look at for further confirmation of ID.