Artorias I suppose. Sanctuary Guardian only took me two attempts. Manus I took down on the first try. Kalameet is only difficult if you are going for her tail. Artorias put up the best fight, taking the most attempts.
"Do you have the courage to ride with the devil?" Now Watching: Kamen Rider Wizard, Kamen Rider OOO, Kamen Rider Ryuki
I died the most to Kalameet trying to knock off his tail. My biggest problem with Manus was finding, summoning, and keeping alive Sif. Artorias ended up being toughest for me, actuallly. It took me awhile to get my equipment straightened out.
Kalameet was a little underwhelming. For all the hype present about him, you'd think it would be a truly terrifying fight, but his attacks are terribly telegraphed. Manus always gets me with his deceptive range and the occasional dark magic spam.
The silver pendant takes the sting out of his dark attacks barring the dark rain (it just clumps up and falls on you anyways) so that part isn't too bad.
If I keep activating the pendant over and over can I just keep it up indefinitely until he's done using his dark attacks?