I just thought of a crazy fanfiction story, what if the Diamonds and the Irkens start a war against each other in order who gets to control the Cluster, while Steven Universe, the Gems, Dib, and Zim (yes, even Zim has to make an ally with these guys because of Tak) trap in middle of a cross-fire and facing both enemies. Think about it, an army of superpowerful Gems vs an army of technologically advanced Irkens.



Maybe Tak, the "female" Tallests, and the Yellow Diamond are the best antagonist on my list.