Someone who dislikes everything and everyone and constantly voices his criticism of everything/everyone. This person is often angry with others for offending him in some way and his CONSTANT griping will mark him as a "hate-asaurus rex" rather than merely a "hater." Additionally, a hate-asaurus rex typically calls other people "haters" in an effort to disguise his "hater" comments.
Gina: Hey! Stop being such a hate-asaurus rex!