Someone that doesn't try within the context of the situation they are in. If you're doing 4-man dungeons, just try to be acceptable to the point of not being a detriment to your group (as in being overall more useful than someone that is AFK). If you're doing harder content, same rules apply but in a stricter sense.

Quote Originally Posted by Amiaze View Post
I don't think the question is specific enough. There's a difference between a "bad player" and a "player you don't want to play with".

I've been with players who could heal and DPS with the best of 'em, but their attitudes were so terrible that you just didn't want to be around them, eventually. Great player, but not great to play with. On the other hand, I've run with people who didn't know how to silence or stun and who turned mobs towards the party rather than away from it, but whose /smile could light up the whole dungeon. They weren't great players, but they were great to play with. And if they were willing to learn, well, I was more likely to call them a good player in the long run.
That's more of a context of being a bad person than a player. Think of it like sports. All the bad publicity that athletes get don't make them a bad player of their sport, it makes them a bad human being. Their skills as players make them a good (or bad) player. Their personalities make them a good (or bad) person. I play games with folks that are terrible as players, but it doesn't mean I don't like them as people. I just probably wouldn't recommend them to a group looking to do difficult content.