A Greif artist is some one who is always negative or always taking this piss. Can be to the subjects face or behind his/her back. Also the person displays some skill in the mocking of others.
The God's son, who keeps inconveniencing Twitch streamer and YouTuber DarkViperAU in his "chaos mod" playthroughs of GTA V. Continuesly getting spawned into the game by viewers, or just bad luck.
*DarkViperAU calmly playing GTA V with the chaos mod*, *Griefer Jesus gets spawned in* DarkViperAU: "Oh no! Griefer Jesus! He is going to kill me!"