Jujutsu Kaisen has introduced several cursed techniques, each with rather simple or a more convoluted set of rules and limitations. Although most of the techniques belonging to the main and supporting cast ended up serving as integral tools throughout the major fights of the series, Geto's own cursed technique is often cited as the one technique that went underutilized.
While Geto didn't have a domain expansion, with his maximum technique serving as his "final move", he did have the special grade spirit Tamamo-no-Mae, which should've served as his strongest familiar.
Although the tamed cursed spirit ended up being a fodder in front of Yuta as well as Rika, her original folklore inspirations and the rumours associated with this figure could've made her into one of the strongest entities to ever debut in the series.
Disclaimer- This article contains spoilers for Jujutsu Kaisen and reflects the author's opinion.
Jujutsu Kaisen: Tamamo no Mae's actual folklore and its underutilization in the series

Suguru Geto's Cursed Spirit Manipulation was first introduced within the Jujutsu Kaisen 0 series, at the height of his campaign against non-sorcerers. While Tamamo-no-Mae made her debut preceding the reveal of Geto's maximum technique, the tamed cursed spirit was revealed as one of the few special grade curses in existence.
Tamamo-no-Mae incarnate was directly inspired by the actual Tamamo-no-Mae folklore, which has gone on to inspire numerous different media throughout the ages. According to real-world myths, Tamamo-no-Mae was a sorcerer born in China during an era preceding the Heian Era by centuries.

Tamamo-no-Mae has been depicted as a rather vengeful spiritual entity, directly being the reason behind the toppling of numerous dynasties, while also serving as the main culprit behind numerous massacres throughout the ages. Eventually, she reached Japan and followed her usual tendencies to enact widespread disasters, until she was sealed or contained towards the end of the Heian Era within the structure known as the "Killing Stone" or "Sessho-Seki" in modern-day Japan.
While her usual interpretations do not usually depict all of her forms, it should be noted that she is also associated with the nine-tailed fox yokai myths that have served as the basis for folklore for many centuries. The folklore figure maintains relevance in the current era, exemplified by the splitting of the Killing Stone in the year 2022 made headlines throughout social media networks.

Given the spirit's perceived history and apparent massacres starkly dwarfing Sukuna's own known reign and tragedies, it is clear that her position was underutilized within the actual series. While the series makes it clear that the Tamamo-no-Mae Geto controlled was an Imaginary Vengeful Cursed Spirit manifested due to the collective fear towards its legend, the same legend also makes the spirit out to be on par, if not a more malevolent force, compared to Sukuna.
The numerous media related to Jujutsu Kaisen also mention that cursed spirits gain sentience and intelligence according to the level of fear they command. Given that Tamamo-no-Mae stands as one of the most feared evil spirits even in real life, her actual role in the story ended up being lukewarm, with her entire concept being underutilized.

Suguru Geto's lack of a proper "ultimate technique" makes this issue even more grave, especially considering that Tamamo-no-Mae, according to legends, was active throughout the Heian Era. An era that gave rise to the curses and sorcerers standing far above anything that the modern age has produced.
Much like Kenjaku, Tamamo-no-Mae could've similarly been used as a glimpse into pure malice, while simultaneously increasing the danger that Kenjaku or Geto possessed.
Final Thoughts
Jujutsu Kaisen ended with Geto's Cursed Spirit Manipulation remaining as the most underutilized technique within the series. Although the story doesn't go into detail about Geto's cursed technique, it is possible that anime-original scenes expected in Jujutsu Kaisen season 3 deliver the detail that Cursed Spirit Manipulation deserves.
Related links-
- Did Jujutsu Kaisen have a happy ending? Ending explained
- Who is Tengen in Jujutsu Kaisen? Explained
- When does Jujutsu Kaisen manga end? Final chapter details explained
- What is Utahime's power in Jujutsu Kaisen? Explained