what of my "Piercing Cold" example?
I know of zero cold damage spells that don't allow a save, so the point is moot. (Though I would like to hear of one. That build never spent much money, so items of spell immunity to particular spells might be handy.) But yes, if it didn't allow a save, piercing cold could damage him.
Assuming you have nothing preventing a ranged touch attack,
a "Piercing Cold" Polar Ray could deal upwards of 25d6/2 even to an immune monster. No saving throws involved.
I also doubt the Warforged can beat a Wizard in a Control check (INT based), so
a sphere of annihilation remains a perfectly valid, if expensive, way of putting the Juggernaut to rest.
A cleric could also polymorph themselves in a girallon and use its four arms to simultaneously wield 4 +5 composite bows (+4 composite bows enchanted through Greater Magic Weapon), plus Weapon Focus (Composite Longbow) and Rapid Shot, stack +5 arrows and Bracers of Archery on top of that, cast Maximized Cat's Grace and add a Mithril Chain Shirt of Speed, as well as Divine Power, Divine Favor, Righteous Might and Bless for a total of
+38/+38/+38/+33/+28 attacks, each dealing 26 piercing damage... How about it?
Likewise, a Red Wizard leading a full Circle has a total CL of 40, add in Earth Spell and they can gate in a hecatoncheires completly under their control; I wonder how the Warforged would fare against
100 +5 Greatspears hitting it simultaneously.
I also forgot Holy Word and Blasphemy; a Cleric can use Prayer Beads, levels in Hierophant, the Good domain, among others, to boost his CL 10 above yours, in which case these spells would
instantly destroy the Warforged. They are not death dffects, so, death ward and its likes won't help against it.