Mother Spheresaurus vs Megalothor

[Kaijuking101]

https://ultra.fandom.com/wiki/Sphere#Spheresaurus

vs

https://ultra.fandom.com/wiki/Carmeara#Second_Form

Rules:
Second Form Megalothor.
All feats from TV shows they appear in respectively. Sphere Megalothor's feats do not apply to 2nd Form Megalothor as Sphere Megalothor is explicitly noted to be enhanced by the Sphere and stronger than 2nd Form Megalothor.
Scaled.
Mother Spheresaurus as of Episode 25 (having absorbed some of the Eternity Core's energy)
Mother Spheresaurus does NOT have assistance from any Sphere Soldiers or other Sphere.

Verdict:
Tough choice but based on power creep and scaling I would vote Mother Spheresaurus. She's explicitly the strongest Sphere Monster, which would put her above Sphere Megalothor in raw power, she's easily more durable given how Dynamic Type Decker couldn't do a thing do her even when he was empowered by the Eternity Core's energy, for reference Dynamic Type Decker with no empowerments utterly destroyed Terraphaser during his debut, which was undestroyed, and had no physical surface damage apart from being shaken, by a finisher from the Ultra Dual Sword, the same sword which could hurt and threatened to destroy Sphere Megalothor. Whilst Megalothor's arsenal of dark powers and attacks make her more versatile than Mother Spheresaurus, the Mother Sphere's sheer durability and firepower should net her the win, even if she was underwhelming for all the hype they built up around her in the previous few episodes and basically did nothing noteworthy.