The Inhumans are similar to mutants in the Marvel Comics world. The big difference is that they were not born with their powers but were given them. The Inhumans go into a chamber and are exposed to Terrigen Mists, where they receive their powers.
When the Inhumans do get their powers, the person learns their place in the caste system on Attilan. They are either put into a position of power or they are sent to the lower levels and put into the workforce where they can never rise above that level. There are exceptions, mainly with Inhumans on Earth, but when it comes to most Inhumans, the most powerful are the most influential.
Triton
Triton was a member of the Royal Family, the cousin of Black Bolt and Karnak's brother. He is one of the most powerful and strongest Inhumans in the world — but only when he is underwater. When Triton comes out of the water, his skin dries up and he will suffocate in minutes.
This keeps him below a lot of Inhumans because he can only remain powerful underwater. He still ranks above most because when underwater, he can hold his own against Namor, considered the most powerful underwater hero in Marvel Comics.
Reader
Reader is extremely powerful, but he is easy to underestimate because nobody really sees his powers in action. Reader was initially part of an Inhuman tribe that settled on Earth and the power he gained via Terrigenesis was the ability to make anything he reads come true.
There are two limitations to his power that keep him from being overpowered. One is that he only gets three reads a day and the third is always weak. The second is that his enemies gouged his eyes out so he couldn't read. However, his powers even work with brail. They allow him to rewrite reality and even create people, which he did with Daredevil.
Gorgon
Gorgon might be one of the strongest of the Inhumans. He is also a member of the Royal Guard and a loyal ally to the Royal Family. While not related to Black Bolt, he is considered a member of the Inhumans when the comics present them as a team.
A mighty warrior, Gorgon will do anything it takes to win in a battle, and he will never quit. While his strength is great, it is his unbreakable will that keeps him ranked among the most powerful of the Inhumans.
Crystal
When Crystal first appeared in Marvel Comics, she wasn't known for her powers. The girlfriend of the Human Torch and the ally of the Fantastic Four, she was never up to the level of other Inhumans. However, her power levels are in fact great and have her as one of Marvel's most powerful female heroes.
Crystal can control all four elements — water, fire, earth, and air. She can fly, create fire, freeze things, control lightning, cause earthquakes, and more. She has powers that equal several heroes in Marvel and DC, and she has it all in one package.
Ahura
Ahura is one of the newest members of the Inhumans, the son of Black Bolt and Medusa. Ahura started displaying his powers from a young age and after undergoing Terrigenesis, he developed telepathy, flight, and the ability to shoot optic blasts.
By combining and refining his powers, he was able to control others' minds and possess people's bodies. However, he is often unable to control his powers and is still young and unpredictable. If he gains more control when he grows up, he could become one of the most powerful Inhumans in the future.
Quake
Quake broke out thanks to the Agents of S.H.I.E.L.D. TV show. She was Daisy Johnson, whom Agent Phil Coulson convinced to join S.H.I.E.L.D. and become a top agent throughout that series. But she actually debuted in Marvel Comics nine years earlier as a S.H.I.E.L.D. Agent.
In the comics, Daisy never needed to go through the Terrigen Mists like normal Inhumans since her mother was an Inhuman and her father experimented on himself before she was born. Her powers allow her to send out vibrations that can have the power of an earthquake. She ruptured Wolverine's heart once, showing how intense her powers really are.
Maximus
On ABC's The Inhumans TV series, Maximus had no superpowers. The brother of Black Bolt hated him and wanted to take the throne, jealous of his powers. That is not the Maximus from the comics. Known as Maximus the Mad, he is a telepath.
Maximus has the powers to manipulate minds as well as other basic telepathic powers, including image projecting and manipulating someone's personality. He has bouts where he struggles to maintain his sanity, but when he is in control, almost no one can withstand his powers outside of his king and queen.
Medusa
Medusa is the Queen of Attilan and one of the most powerful Inhumans in existence. She also possesses great political powers and took over the ruler of Attilan when Black Bolt found himself exiled. As for her superpowers, they are great with or without her political position.
Medusa's powers come from her hair. She can control every strand of it and have it do anything she wants. It is also strong and resistant to attempts to cut it, unlike The Inhumans TV series. Add to the fact that she is a fierce warrior and a tactical genius, and Medusa ranks as one of the most powerful Inhumans.
Ms. Marvel
Ms. Marvel is a teenager on Earth who gained her powers when the Terrigen Mists was released over New York. She was never part of Attilan and never intended to go there after she gained her powers. What makes Kamala Khan so notable is that she is one of Earth's most powerful heroes.
She can morph her body into any size and shape. Unlike Reed Richards, who mostly has stretching powers, Kamala can gain intense strength and power when she morphs. She can also change her appearance to look like others. More importantly, she has an accelerated healing factor. Kamala has only one weakness in electromagnetic pulses, but she remains an extremely powerful hero.
Black Bolt
From the start, the Inhumans always put the genetically most powerful warrior in the role of king. Black Bolt inherited the role when his parents died, but he more than deserved it. He has one power and it is one that can destroy worlds.
Even a whisper from Black Bolt can cause earthquakes and mass destruction. If he screams, his voice could rip an entire planet in half and destroy it instantly. As a warrior, he has fallen to a few major names like Hulk and Thor, but he just needs to say one thing and he can bring anyone to their knees.