Remove the lore, and having killed them or not.
THESE VIDEOS CONTAIN SPOILERS! If you haven't beaten either and don't want to know what happens to them, don't watch the videos
Deathwing
http://www.wowwiki.com/Deathwing
http://www.youtube.com/watch?v=bYeOtY3sCD8 Deathwing raid cut scenes
OR
Zhaitan
http://wiki.guildwars2.com/wiki/Zhaitan
http://www.youtube.com/watch?v=JDVp__KIfKE Zhaitan fight cut scenes