The Kais are celestial beings who have been assigned to govern different quadrants of the universe. The Kais also have a ranking and hierarchy system which classifies both their position and importance. They are considerably powerful deities with various techniques such as materialization, telekinesis, and telepathy. The most fascinating skill and ability that they have is the ability to create life, as they are the ones that keep watch over all living things. They are responsible for keeping record across their assigned quadrants and sectors, while some of the Kais even have abilities unique only to them that allows them to fulfill their duties more appropriately.
11 South Kai
During his time in otherworld after the Cell Games, Goku travels to the Grand Kai's planet in order to receive special training. The Grand Kai decides to settle this decision by holding a tournament and training the victor as a reward. Every Kai brought some of their best fighters but the South Kai’s warriors were easily outmatched by every fighter. This makes him stand at the bottom of the list because his training was insufficient and unable to help his fighters secure victory. He is also greatly mocked by all the other Kais despite the standard boasting and mocking they do.
10 East Kai
The East Kai is more or less at the same level as South Kai, but because her fighters were somehow able to clear the qualifiers and even obtain victory for a significant number of battles, this at least proved that her training methods were efficient and effective to a certain degree.
Her fighter, Aqua, was able to keep up with Goku who, despite holding back, was still one of the strongest fighters participating in the tournament. She even forced him to get serious, which proves that her training and capabilities were enough to make it worth Goku's time.
9 West Kai
Probably the most obnoxious and self-centered person you’ll see in the Dragon Ball Z series, the West Kai considers himself the top dog among the four Kais and has a rivalry with North Kai (King Kai) about being the best. He gets the 8th highest position due to his fighters reaching the quarter, semi, and final rounds of the tournament. His fighter, Pikkon, went toe to toe with Goku in the final round and was able to hold his own against him even after he had transformed into a Full-Power Super Saiyan. Therefore, it is evident that he is clearly stronger than both East and South Kai.
8 North Kai
North Kai, also known as King Kai, is the governor of the north quadrant and a big part of the series. He is the strongest out of the four Kais because his fighters showed exceptional skill despite seeming more human than the others. His fighters also reached the semi and final stages of the tournament. He mastered the ancient technique, the Spirit Bomb, and created his own physical ability boosting technique, the Kiaoken, which have both become two of the most iconic techniques of the series. They are an integral part of Goku's arsenal to defeat almost a villain he otherwise has difficulty against.
7 Grand Kai
An old looking man who seems quite similar to Roshi in terms of personality, the Grand Kai is the one in charge of overseeing the four Kais and is hinted at being far stronger than the four. He is both the teacher of some of the greatest warriors in the universe and one of the strongest warriors himself.
However, due to a lack of evidence, we can not deduce the complete potential he has or his fighting ability. Nevertheless, he is quite powerful given the position he holds and even seems confident enough to reach Goku’s level (Cell saga) after two hundred years.
6 Elder Kai
Old Kai, or more frequently referred to as Elder Kai, is the former Supreme Kai of Universe 7. After being fused to a witch by accident, Elder Kai gained magical abilities. He may be physically weaker than the others but his place on this list is purely because even though he has lost some of his godly powers, he is able to tap into an individual’s hidden potential and unlock it completely. Basically, he can bring out the best in someone without them having to do a single thing. He can also materialize certain objects and items.
5 Alternate Universe Supreme Kai
As the story of Super continues, we learn more about the hierarchy among the Gods and how it works. The hierarchy is similar to a military set up where there are multiple overseers and higher-ups, that each one has to report to regarding their universe. They are not greatly elaborated on but with the information that has been provided via episodes and manga publication, it is confirmed that they are strong enough to defeat Frieza (Pre Super) in a single blow. Lack of data places them just above the Old Kia until more details are revealed.
4 Shin (Supreme Kai)
Like his fellow supreme Kai, Shin is the serving overseer for Universe 7 and is quite strong as well. He is among the Supremes, which means that he is strong enough to defeat Frieza, before the events of Super, with a single blow.
He is ranked above the other Supreme Kais because of the fact that we have seen him in action when he first appeared in the Buu Saga, which gives us more insight on his power and limitations with respect to the others. He was also able to briefly engage Zamasu who is one the strongest antagonists through the series.
3 Grand Supreme Kai
A position that has only been shown during the Buu Saga, the Grand Supreme Kai stands atop all the other Supreme Kai and is their overseer. The specifics of this position have never been elaborated on, and the only data we were given is his battle against Kid Buu. He is powerful enough to fend him off, and he even cut off and disintegrated his arm. He did this while Shin was easily beaten by Kid Buu in one or two moves. It is certain that he is far superior to his junior and his power is one to be impressed by.
Like Android 21, Chronoa was introduced as one of the main characters in Dragon Ball: Xenoverse. It is debatable whether she is canon or not because she did not appear in the manga or anime, but she is still considered Kai. Chronoa, like her name states, is the Supreme Kai of Time. Her job is to oversee the flow of time, removing any rogue or tampered timelines and temporal anomalies. Though she is considered as powerful as her fellow Kais, her time control ability edges her ahead of the Supreme Kai and possibly even the Grand Supreme Kai as she works without restrictions.
It's debatable whether or not Zamasu is a Kai himself. He was technically shown as a Kai apprentice, and the Potara Fusion he underwent was permanent, which is only unique to Kais. Originally the same as the other Kiaoshin, Zamasu trained himself to focus his energy into his hand and form a blade which is one of the strongest energy weapons in the series. Goku himself states, after beating him in a spar, that even Shin would not have stood a chance against him. Goku himself couldn't handle him very well as Zamasu had incredible adaptability and learning capability.