I'm running Carrion Crown, and my group's gotten to Harrowstone prison, where they're fighting the animated scythe on the west balcony. Being an animated object, it's treated as a construct, but it also has the haunted flaw, which reads as follows:
Haunted (Ex, +1 CP): The object is haunted by a malevolent spirit. It takes damage from positive energy as if it were an undead creature and can be detect by detect undead.
Ordinarily, energy attacks do half damage to objects before applying hardness, but there is the caveat that some "particularly effective" energy types might do full damage before hardness, and I can see that caveat applying here. But in both cases, hardness still applies - in this case, would the "takes damage from positive energy as if it were an undead creature" override the animated object's hardness? The answer makes the fight very different - from difficult to a one-hit wonder.