Since there are 10 episodes, there is not much time to develop these characters so I am going by their significance in Sentai, more than their overall significance in Power Rangers. Also, I am comparing Lord Zedd and Scrozzle to Sentai characters that are alike, but not necessarily inspired by.
Lord Zedd/Jark Matter
Lord Zedd is not inspired by Jark Matter but fans thought they would use the suit for the final form of Lord Zedd. Jark Matter is the Kyuranger main villain. The similarity is that they both have brains exposed. Both wanted to take over the universe. Jark Matter was destroyed and Lord Zedd was handled with humanly, having to live his nightmares on a planet. Lord Zedd had a soft spot for Ollie.
Ikargen/Inkworth
Both were very gentlemanly, Ikargen is calm and calculated. Inkworth is a butler but fights the Rangers very toughly. Inkworth seems to think of himself not in the best light. Mardakko is Ikargen; 's partner, she is absent in Power Rangers.
Bajillia Naire/Madakko
Madakko is Ikargen's partner and she has around five to six lives in Kyuranger. Many fans think Bajillia is inspired by Madakko because they are both squid-inspired. It is likely the costume for Madakko wore off with time and wasn't usable and Hasbro wanted to create new characters. I don't know the truth. Brajillia is the mastermind behind the whole operation of CEO of Squid Ink. She is the mother of Squillia. She cares more about her looks and optics. Barjillia and Squillia are AMerican made.
Scrozzle/Finster
Scorzzle is American Made and was introduced in Beast Morphers, he appeared sporadically in Dino Fury. He very much is like Finster, creating devices and monsters. Finster wasn't never destroyed, and neither was Scorzzle.
Krymzo/Scorpio
Scorpio was the Orange Kyuranger's brother who became evil, they fought and in the end, he was destroyed. He had an important arc that fans loved. Unfortunately, Krymzo was only in 2 episodes and was just a dancer who was quickly dispatched.
Kuervo/Omwhyzo
Kuervo was a hero ally of the resistance that betrayed the good side and sided with Jark Matter and merged with a villain. Omwhyzo is a general who deals with Squillia and is defeated by Tarrick. I liked the character and wish we saw him more.
Deathworms/Scuttleworms
There were different Deathworms and Scuttleworms. Deathworms were more of pets and used as minions. Scuttleworms were inhabitants of their home planet who had babies and were disturbed by the Rangers. It is debatable. I mean, they had to footage of the zords fighting these worms and they had to have them in space, so they had to find a way to make a story. So the story they made up was they were hostile creatures.
Jozotic/Bangray
Bangray was one of the generals from Zyuohger. Simon Bennett said that Toei gave them some suits from other shows, even if they weren't adapted into Power Rangers. I don't know if they gave them suits to choose from, or just sent whatever suits they had available. Toei had intended to clear out from their warehouses and the suits were given to Hasbro before its discarding. Joztic was a villain who helped Ollie fight the Rangers and ultimately just disappeared and wasn't seen again. I would have liked to see him more with Ollie if they had more episodes.
Jadana/Naria
Naria was one of the generals from Zyuohger. Jadana was just a dancer who was quickly dispatched by one of the Rangers.