For me: hackers. In the last 2 months I die by hackers every day I play. It's ridiculous. I like to PVP on public servers but they always have hackers. Invisible players, killing through walls, teleporting, etc. And the main problem is that they are growing in number. Server admins can't ban them and the devs should be more effective on this subject. They talk about ban waves but the game needs some waves now...