User blog comment:Zack Tan/Volume 9 Intermission./@comment-33177490-20150823172503/@comment-70.160.109.135-20150824035822

Ainz worst nightmare was Shalltear. She specialized inflicting crush damage and using holy spells, while possesing high resistance to death magic. Plus she had insane HP and a ressurrection item. The only reason why Ainz won against her, is because he knew all her abilities and attack patterns, so he forumulated a battle plan to exploit her tactics.

Most other holy users, don't also possess immunity to Ainz's death specialties. Shalltear was supposedly a rare example -- and the reason why he mused if Peroroncino made her specifically to defeat him.