There are very few coaches who could make a Top 5 list in franchise history for multiple teams, but Mike Keenan would be one of those few coaches.
Mike Keenan is probably the last true jerk for a coach in NHL history, and he always leaves the franchise with pretty much everyone hating him at the end of his tenure.
One thing that Keenan could do in his younger days was get teams to at least the Conference Championships.
He was able to get the Philadelphia Flyers his first NHL team to the Cup Finals without being able to seal the deal.