That finale was pretty weird : because frankly, I've never seen a Big Bad be so happy of losing : first, when he sees the light shining in the darkness, he sees it, not as an annoying stuff, but as the return of a memory that has been important to him. Then, when he sees the Rainbow Line trains charging against his darkness and his castle, he looks at it with fascination and even pleasure: Mork has to push him aside because otherwise, he would have let himself been caught by the trains.
When Right and the others are facing him defiantly, is he annoyed? not at all, in the contrary, he likes Right much more full of shine and brightness than the Right full of darkness before : we see him laugh after Right tells him he's gonna use imagination, not darkness against him : not really a mocking laugh, but a laugh of admiration, even in a way, respect.
And while indeed, he faces him in a tough showdown, one has to wonder if the reason Zett wanted to defeat Right wasn't linked to the fact he was overcome with darkness. It's telling that he hates Nero and Morc much more than his enemies : there is no gratitude to them when he takes their darkness, he wants them gone, much more than the Toqger. It's very telling that, after the final blown he reveives from Right, he's not angry at all, but he seemed even at peace, admiring a rainbow, appreciating the light he in fact loves.
Kobayashi wanted the audience to have sympathy for Zett, and it's not surprising he survives.
The most striking element is the fact Gritta (or should I say "Glitter", because it's her real role : being a light shining in the darkness, an entity which "glitter", like a star in the night) is alive : when you think of it, it meant that Zett protected her from Nero and Mork's wrath in episode 45 by pretending to kill her. It makes wonder if in fact, what Zett really wanted was to get rid of his generals, to be at last left alone, and not under pressure from them, and be able to stay with Gritta afterwards, who is indeed the only shining he can get in the world of darkness he must live in.
Other point : while the return of the 4 other primary Toqger is seen as a key point of the show, in fact, their role was pretty limited in the final showdown ; they mostly fight an irrelevant duel with Morc (since in fact, Morc's death is Zett's work) and they give their resshas to Right for his final duel with Zett.
Lastly, the final scenes pretty much solve every problem incredibly easily : not only the Toqger are recognized by their family as adults, but they are even able to become kids again, as if nothing had happened : pretty much the opposite way Go-Busters did. While that ending is still very emotional, it's pretty much a "safe" ending.
A fun finale, but Toqger feels really like a very "safe show", and probably one of the most light hearted sentai ever done.