Since this is just about their journey in regards to slaying, not includng their personal lives don't count Buffy having to kill Angel, because that wouldn't have been hard if she didn't love him, so that was a trial on a personal emotional level.

As a slayer I think Faith's journey was much more difficult than Buffy's. She's immediatly the second slayer, and considered kind of a back up slayer with Buffy the 'real' slayer, then she began abusing her power, then reformed and became a hero. Her understanding about what being a slayer means and the way she uses her power has been the most dramatic journey I think.

I don't think that Kendra had enough time or opportunity to develop all that much :(

And I'm not sure Buffy ever really 'rejected' her calling, she always fort (apart from when she was in LA really, but like you said candrani, that was for emotional reasons really) she just resented having to be the slayer and have all of the responsibility of protecting the world.

Faith struggled with the power she inherited and what that she could do with it. It took her a long time to adjust and come to terms with it. And only after a long time of reflection and fighting herself could she be a 'proper' slayer.

In the first episode Buffy tells Giles she's retired and won't be the slayer anymore. It's not till Willow gets attacked that she starts slaying. that's what I meant by rejecting her calling.

And I agree poor Kendra didn't get the time to develop. I'm always torn about that because I liked Faith more but I also would have liked to see more of Kendra. It was the first time we had really seen a slayer who had dedicated her life to slaying and fully accepted it and lived how the council expected.

See even when Buffy says that to Giles in the 1st ep I think it was more of a knee jerk reaction. She had just moved and started at a new school, she wanted to fit in and get the lay of the land. After everything she had been through before coming to Sunnydale she knew she couldn't really escape her calling and now she had really support from Giles. I'm not sure she would have ever truly quit!

buffy has saved the world so many times!!! she should get a medal!!!