No Idea if this was intentional or not but I noticed an interesting parallel between the endings for Kuuga and 0-1 where both their climaxes focus on an internal conflict, with the main rider’s very soul being at risk.

At the end of Kamen Rider Kuuga Godai unlocks his final form, Ultimate Form, a terrible power capable of either saving or destroying the world. While in this form Kuuga must maintain a pure heart or else become the Great Darkness. Yet despite the risks Godai has no choice but to use it against the leader of the Grongi, N Daguva Zeba, as it is the only power capable of defeating him. So in the final battle of Kuuga Godai not only has to defeat N Daguva Zeba but keep himself from falling into darkness. He must not be give in to the temptation of power or hatred. A feat all the more difficult when N Daguva Zeba not only loves to indulge in the senseless violence, but is actively provoking Godai in hopes of witnessing the Great Darkness. Ultimately Godai’s feelings boil over and the glorious battle between two gods is reduced to just two bloody men beating the crap out of each other. Godai, shedding tears as he simply wishes for the conflict to end, whereas N Daguva Zeba uses his final breath to laugh like a madman. In the end Godai is able to defeat both N Daguva Zeba and his inner demons, saving the smiles of everyone, including himself.

0-1 is where things get interesting as its final arc shares a lot with Kuuga. In the last four episodes The main protagonist Aruto Hidden faces a great tragedy. His partner, The Humangear Secretary, Izu dies at the hands of the radical Horobi, after she attempted to persuade him against his war on humanity. With Izu killed in such a cruel and senseless way Aruto hits rock bottom and gives in to his own malice. Aruto becomes the reincarnation of The Ark, Kamen Rider Ark-One. Just like Kuuga Ultimate Form, it is a dark version of the titular Zero-One capable of destroying the world. Where they diverge however is in how the perspective powers influence their central riders. Ultimate Form’s power comes with the risk of corrupting its wielder, whereas Ark-One has no influence on its user. That's Right unlike Godai, Aruto is in complete control of himself and his action while fighting as Ark-One. Using the power of malice, fighting his friends, and seeking revenge against Horobi were all Aruto’s choices, not the will of The Ark or Azu. This ultimately reframes the climax of Zero-One from its heisei era counterpart. Kuuga was about Godai resisting temptation. Whereas 0-1 is about Aruto dealing with the consequences of giving in.    

In the Final battle of 0-1 Aruto has lost his innocence, his dreams, the hope of humanity, and the trust of the Humagear. Yet he still fights. With both Aruto and Horobi using the Power of Ark in the face of their grief they risk an all out war between Humanity and Humagear. However as the fight goes on it is revealed that Aruto’s motives have changed. Instead of fighting for Revenge Aruto seeks to save Horobi. To help the man express his grief and accept his own humanity. Displayed best as Aruto allows Horobi to destroy the Arc-One suit. Ultimately the battle between Aruto and Horobi ends with the reveal of a form that goes beyond the tradition of the Final Form, Realizing Hopper. Realizing Hopper is the manifestation of Aruto’s ideals in the purest form. Showing that they were never truly lost in Aruto fall, but instead have grown stronger thanks to his renewed determination. Realizing Hopper grants Aruto the power to forgive Horobi, freeing him from the Ark’s influence and cleansing both riders of the sins. By saving Horobi’s soul Aruto paves the paths towards true peace between Humans and Humagears.