Dawn was subjected to something different. The house was trashed in successive blasts of energy and a demon (actually a guy in the same demon suit as Gnarl from Same Time, Same Place 7ABB03) was shown to be attacking Joyce. Joyce was Dawn's mother whereas Cassie was not related to Willow and only claimed to carry a message from Tara.
My vote is for Dawn being subjected to the most cruelty.
[MENTION=8356]HisMrs[/MENTION] -- From what I have read, Amber Benson wasn't available to appear in this episode so they chose Cassie's character. I think they picked her because she had recently been introduced to the audience and was fresh in our minds. Someone like Jenny Calendar would have been confusing to those who did not see the 2nd season of the series. Also, it seems like the First favored appearing as the more recently deceased.
I know Amber wasn't available... She also said she didn't want to taint Tara's character by appearing as an evil character.
And as far as The First appearing as "recently deceased" people, I never got that distinction; I thought The First just wanted to appear as whoever would shake the characters up more, hence coming as Joyce, The Mayor, etc. The First went for the emotional blows more than anything else.
Which do you think was the cruelest in Conversations?
The First posing as Cassie Newton from a message from Tara in the Afterlife.
The First posing as Joyce Summers to Dawn
which was the Cruelest