As far as I understand, Jung used the term “crucifixion of opposites” at least once in writing, possibly twice, in a throwaway fashion, although I personally arrived at the term (which is central to my work) independently. The first reference I’ve seen is in a letter to Olga Frobe-Kapteyn on August 20, 1945. He wrote:

“Dear Frau Frobe, the opus consists of three parts: insight, endurance, and action. Psychology is needed only in the first part, but in the second and third parts moral strength plays the predominant role. Your present situation is the result of pressure of circumstances which are unavoidable. It is conflicts of duty that make endurance and action so difficult. Your life's work for Eranos was unavoidable and right. Nevertheless it conflicts with maternal duties which are equally unavoidable and right. The one must exist, and so must the other. There can be no resolution, only patient endurance of the opposites which ultimately spring from your own nature. You yourself are a conflict that rages in itself and against itself, in order to melt its incompatible substances, the male and the female, in the fire of suffering, and thus create that fixed and unalterable form which is the goal of life. Everyone goes through this mill, consciously or unconsciously, voluntarily or forcibly. We are crucified between the opposites and delivered up to the torture until the "reconciling third" takes shape. Do not doubt the rightness of the two sides within you, and let whatever may happen, happen. Admit that your daughter is right in saying you are a bad mother, and defend your duty as a mother towards Eranos. But never forget that Eranos is also the right thing and was latent within you from the beginning. The apparently unendurable conflict is proof of the rightness of your life. A life without inner contradiction is either only half a life or else a life in the Beyond, which is destined only for angels. But God loves human beings more than the angels. With kindest regards, Yours sincerely, C.G Jung”

Jung is correct here as far as it goes. However, I extend beyond his statement where I believe that life is inherently crucified between the opposites as a base condition of living. This is because (1) energies in this reality are defined in terms of its opposite (good and evil, light vs darkness, up vs down, in vs out, hot vs cold, mercy vs justice, love vs hatred, an infinite number of such pairings), and (2) the lived navigation of the opposites within finitude is what gives life meaning to unconscious totality, because consciousness arises from subject/object differentiation which are otherwise united within it.

Jung puts a redemptive spin on this, seeing the Self as navigating an individual teleologically with “love” toward wholeness, whereas I see the Self as an orienting center which offers a provisional foothold, tested and re-tested, not a guaranteed eventual arrival - many people fail or collapse on their journey - and that all experiences add to totality whether or not redemption occurs.

Thus it seems to me that for Christianity, the Cross is one historical event, for Jung, the Cross becomes a recurring psychological archetype, while for me the Cross becomes the basic geometry of finite existence itself. Every organism, every choice, every identity, every differentiation, is already cruciform. Selection always entails foreclosure, identity always excludes and life always differentiates, so "crucifixion" stops being a religious image and becomes a description of how finite reality operates. A finite being is crucified because every act of differentiation simultaneously realizes one possibility and forecloses others, and consciousness makes one aware of this to greater or lesser degrees. The cross, therefore, is the intersection of time, choice, and limitation, and you can't escape it because it's what makes existence possible in the first place.

This is why life feels inherently tense, high-stakes, and exhausting: it’s not because a person is doing it wrong or needs therapy; it’s because the very act of being a conscious, finite entity is a state of perpetual tension between what is chosen and what is left behind. This is why my use of the term "crucifixion of opposites" is structural to my work instead of incidental.