Only in his early appearances.
Well, I think even that is debatable.
Q was heavy handed and scared the shit out of the Enterprise crew in Encounter at Farpoint, sure, but he didn't kill anyone. The only time Enterprise crew die as a result of Q's visit, is Q Who, and even then, it was actually the Borg that did it, and Q actually did humanity a favor in the long run, by introducing them to the Borg, so that they could be prepared. Had Q not done what he did, the Borg may have conquered and assimilated the Feds.
In fact, from a certain point of view, he actually helped Picard discover the "mystery" of Farpoint station, and prevent the Feds from making a treaty with Zorn and his people, who were actually exploiting the creature for personal gain.
Rewatch the last 10 minutes, Q is basically just sitting back, watching everyone on the crew come to their own conclusions, and he seems to be smirking, but almost in a way where he is smiling to himself, that these humans actually do get it.
At first we didn't know Q's motives in that episode, but later on I think Q proves to be somewhat of a Prometheus firgure, more than a Loki figure, and in that light, I think even in EAF, Q is actually helping humanity in the same way he does in AGT: giving a nudge, but letting humanity discover things on their own. He just acts as the foil to Picard, because that is what gets Picard out of his comfort zone.