A bad player for me is someone:

1. Has the skills to do decent damage, but doesnt want to do this, because of reasons. I have met alot of players who completed endgame raids etc, but when playing with randoms they go the lazy route and only use the minimum required skills. Tanks that do not bother with defensive CD, DPS who are lazy and stand in everything and underpreform, healers who have full mana bar and do nothing. For me those players are the bad ones.

2. Toxic players and trolls, players only log in to ruin another players playtime.

I do not count new players, players are new to a content, class or role as bad, because they are learning.