Thinking about it, Zenos is strangely one of the most helpful NPCs in the game

Our battles with him caused us to get stronger without help from Hydaelyn or other plot reasons.

He contained Shinryu until we got strong enough to defeat both him and it saving us dealing with a powerful primal early on.

He basically left Doma undefended except the bare minimum making it easier to liberate.

He killed Varis and stopped Black Rose from being deployed.

He caused the collapse of the Garlean Empire.

He helped us defeat Meteion.