Unless there is a Good Friday in our lives there will never be an Easter Sunday; unless we die to this world, we shall not live to the next; unless there is the crown of thorns, there will never be the halo of light; unless there is the cross, there will never be an empty tomb; unless we lose our life, we shall not find it; unless we are crucified with Christ, we shall never rise with Christ. Such is the plan, and on our choice, depends eternal issues.
—  Fulton J. Sheen

So, apparently, crucifixion in Super Sentai is a trope going all the way back to the first series, Himitsu Sentai GoRanger. This did not get started with Sentai though as Crucifixion in Toku dates back to at least Ultraseven* in 1967:

Perhaps even more (in)famously is the scene from 1972′s Ultraman Ace where the Ultra Brothers are crucified on the Planet Gologotha as a trap for the new hero.

This scene is actually so famous in the series that it got a scene set release in the Ultra Act toyline from Bandai.

I think this got started because the creator of Ultraman and Ultraseven, Eiji Tsuburaya, was a Catholic who liked to infuse Christian religious imagery into his work.  The classic Ultraman specium beam pose is supposed to resemble a cross,  the ultimate ward against evil.

The actual meaning of crucifixion was apparently lost and seen as just a means of restraint before an execution.  Or maybe the meaning was stripped away and the original intent as an archaic, barbaric form of execution restored.

The Super Sentai series above are (in order of the pictures):

Kaizoku Sentai Gokaiger

Himitsu Sentai GoRanger

J.A.K.Q. Dengekitai

Choudenshi Bioman

Hikari Sentai Maskman

Choujin Sentai Jetman

and then two instances from:

Hyakujyuu Sentai GaoRanger

*The episode of Ultraseven featuring the hero’s crucifixion was accidentally aired (in dubbed form) by TNT in the United States on Easter Sunday, an act that upset several of their viewers considering TNT is based in the Conservative Southern city of Atlanta.

Lo que paso en la cruz, no fue el hecho de que a Jesús lo crucificaran, lo golpearan, lo humillaran y lo acusaran injustamente lo que nos hizo salvos, no fue el hecho de que lo clavaran en la cruz solo por predicar el amor de Dios y el evangelio… Porque muchas personas mueren a diario por predicar el evangelio y hay incluso quienes tambien murieron crucificados a causa de esto. La diferencia entre ellos y Jesús es que Él fue, es y será el único capaz de llevar y haber cargado toda la IRA de Dios que mereciamos tu y yo a causa de nuestros pecados. ESA ES LA VERDADERA RAZÓN DE LA SALVACIÓN, que existe alguien que ya pagó el precio aquel, que ni tu ni yo hubieramos podido pagar. #PorSuGraciaSomosSalvos
Gracia: Favor inmerecido, no mereciamos nada pero Dios nos lo ha dado todo.


I lift mine eyes, and see
Thee, tender Lord, in pain upon the tree,
Athirst for my sake and athirst for me.

“Yea, look upon Me there,
Compassed with thorns and bleeding everywhere,
For thy sake bearing all, and glad to bear.”

I lift my heart to pray:
Thou Who didst love me all that darkened day,
Wilt Thou not love me to the end alway?

- Extract from Palm Sunday, Christina Rossetti

detail Isenheim Altarpiece, c.1510-15, Matthias Grünewald