My qualifications to get on my "bad player list" are the following:

- Having a bad attitude. It is quite possible to take a game seriously without acting like a complete jerk when things are not going your way.
- Players that are obviously not trying. I can forgive if you at least have NQ class & level-appropriate gear. RNG can be unkind in those green & pink drops. Also: don't wear NQ vendor gear in raids. It's not a good idea.*
- Bots.

* I experienced this last night. Queued up for Qarn, got an in-progress. Turns out I replaced a bot (or a really bad player... though botters are bad players to begin with) Arcanist that used only topaz carbuncle, worse crafting gear (especially accessories), had a level 1 ring that had crit. The trio were so relieved to not get another bot to replace that Arcanist.