Superheroes in comics seem to be so perfectly "created" that they're often each seen as the most powerful ever. That remains mostly true throughout their careers, but every so often, a new writer will come along and decide that a hero needs a kid - likely creating some sort of powerful child superhero. When that happens, it can be challenging to determine what level of power or even which types of powers those kids will inherit from their folks.
Typically, a child of a superhero or supervillain is handled in one of two ways: they are either given no powers whatsoever, or they are souped-up versions of their folks. In fact, it's a fairly common practice to make the kid even more powerful than their parents - which is a pretty big deal.
Parents: Reed Richards & Susan Storm
Franklin is the first-born child of Mister Fantastic and the Invisible Woman. Because they were fundamentally altered by cosmic rays, which granted them their powers, their children were born mutants. Unlike most mutants, who manifest their changes in puberty, Franklin was born with them, which was something of a problem.
Franklin has the power to alter the very core of reality. If he wants to create a pocket universe before bedtime, he can do that - and he has. Whatever he wants to happen, he can make happen, and while his parents are incredibly powerful, they are nothing compared to Franklin. He is one of the most powerful characters in the entire Marvel Universe, which includes the likes of Galactus and the Celestials.
Parents: Professor Charles Xavier & Gabrielle Haller
David Haller, known more widely as Legion, is the son of Professor X, so you know he has some power hidden somewhere in him. After all, Xavier is the most powerful telepath in the world, but that may have been more of an impediment to young David's genes than a boon. Legion is afflicted with a unique type of Dissociative Identity Disorder, which is somewhat similar to schizophrenia.
Legion has numerous personalities which can come to the surface at any given moment. Each of these personalities is a completely unique individual, and they are all Omega-level mutants. This means that one personality may be able to alter reality while another can travel through time. The beauty of the character is that writers can have him do anything they want, so long as a new personality is created to justify it. As of 2020, Legion has been noted as having more than 1,000 personalities.
Parents: Magneto (not confirmed) & Natalya Maximoff
Wanda Maximoff, or Scarlet Witch, is the daughter of Natalya Maximoff and Magneto... except, she may not be. Her parentage is somewhat muddled due to retconning and other issues, but for most of her publishing history, she was believed to be the daughter of Magneto. Now, Magneto is powerful; he's an Omega-level mutant capable of manipulating the magnetic field of anything. But Scarlet Witch is far more powerful than him.
Wanda has the ability to alter reality, though she often does so chaotically. She initially was shown to possess an ability dubbed "Chaos Magic," but she's been modified over the years to become a woman capable of erasing nearly all mutants from existence. She didn't eliminate everyone entirely, but anyone with the mutant gene lost it, leaving fewer than 200 who still had it. She even created a couple of kids for herself without having to go through the bother of getting pregnant and delivering them. If she really wanted to, she could remove the powers of anyone, take them for herself, or blow up the sun.
Parents: Bruce Banner & Caiera
When the Incredible Hulk found himself on Sakaar, he beat the crap out of everyone until he became the ruler of the planet. Just as he was enjoying his newfound supremacy, the ship that brought him there blew up and took out his wife and unborn child... or so it appeared. When Caiera the Oldstrong perished, a cocoon holding Skaar fell into a lake of fire, and when he was ready, he emerged from that lake as a human boy who quickly matured into a man.
While he does transform into a Hulk, that's not the real source of Sakaar's powers. He possesses the "Old Power," which is an ancient power brought to Sakaar by a society of Shadow Priests. It amounts to an artificial version of the Power Cosmic and is highly unstable. This puts Skaar in the same league as characters like Galactus, though he isn't as powerful, nor does he possess the same level of control. But compared to the Hulk, he's significantly more powerful - and that's saying something.