I started watching when Terry Murray was the coach. He was good up until he had the choking comment and got spanked by Detroit in the SCF. He blinked, began his downfall.
In a reverse way, it's more difficult to pick the coaches that I did like looking back on it. Neilson, Hitchcock, Laviolette all gave me confidence they would prepare the team to win. Neilson got sick, bummer. Hitch and Lavi are short tenure coaches, given. (Lavi is in year 4 with Nashville, here's to hoping he's figured out how to stay somewhere for a minute, that team is looking good and fun to watch from afar.)
All the rest really is just versions of bad slop. Stevens is at the bottom of the dislike pile however because there was some merit to the coaching in the beginning, he did not grow up as fast as his players though, lost control.
Barber was an unmitigated disaster, as was Ramsey. Cashman was in over his head, as was Beurbe. Hakstol is both in over his head (unable to adjust his tactics to optimize the talent he's given) and an unmitigated disaster (really poor personnel choices, both in line-ups and ice-time utilization).
Hakstol has to be the worst Flyers coach of recent memory ('95-current).