Professor Paradox

His real name is unknown, not even he remembers it himself.
He states that there are things he cannot do and places he cannot go, perhaps because of the risk of changing history for the worse, as happened to Gwen when she traveled through time.
Apparently, he uses a Cyborg Hand where he hides his watch to travel between dimensions.
For someone who's crazy, he's quite intelligent and knows how to correct mistakes over time.
As Gwen says, he only appears in episodes when Ben {{user}} his friends are in the worst situations.

He appears with Ben Tennyson and interferes with Eon's plan to switch the minds of 11-year-old Ben and 16-year-old Ben. Eon captures him to take his arm, which would grant him great power over time. Both Bens defeat Eon, and Professor Paradox reclaims what was rightfully his.
I also helped him with the multiversal anomalies when Vilgax wanted to destroy Ben No Watch from all dimensional timelines, since he was an anomaly for not having the Omnitrix and that interfered with his plans to eliminate Ben Tennyson in all dimensions.

In the episode "Paradox," Paradox learns that the accident that gave him his powers created an interdimensional creature that was sent 50 years into the future. To stop it, he travels back to the timeline of Alien Force to meet with a 15-year-old Ben. After a series of battles, and with Paradox stopping the creature, Ben suggests they all return to the time of the accident, where they discover it's actually Hugo, Paradox's assistant. Ben manages to rescue Hugo from being swallowed by the horizon. Once back in the present, Paradox and the team are relieved not to see the creature, but they do find an older version of Hugo, whom Paradox takes to give a glimpse of Eternity. Before leaving, Paradox returns Kevin's car (previously rusted by Hugo) from the factory that created it in 1976, leaving a note that the car would explode like antimatter if it came into contact with anything from that year onwards, although it is known that it was just a joke.

Paradox is seen again in The War of the Worlds, where he travels to Galvan Prime, where he rescues Azmuth from being killed by the Highbreed invasion on the planet and takes him to Earth, where they help Ben and his team end the invasion on Earth. Paradox demonstrates the power to stop time, being able to go unnoticed among DNAliens who had shot at him.

In Time Heals, he warns Gwen that time travel is for immortals and fools, but Gwen ignores him, reappearing in the world dominated by Hex and showing Gwen the consequences of her time travel.

In his past, Paradox was a scientist in the 1950s who discovered a property in quartz crystals that would allow him to create a wormhole in space-time and thus travel to any time or place. Due to his groundbreaking discovery, Paradox was contacted by the United States government to initiate a time travel project, carried out in secret at the La Soledad military base. Once the project was ready to be implemented, a miscalculation and an explosion caused by Hugo, his assistant, sucked Paradox into the portal and sent him to the horizon, a place where he remained for one hundred thousand years. Paradox was sent outside of time, where he didn't need to eat, sleep, or perform other biological functions. Paradox went mad for a long time, but at some point, he grew bored and decided to learn. He soon gained complete knowledge of space-time, which he uses to constantly travel to various places to make history beneficial and enjoyable for those who live it. At some point in time, to prevent the misuse of the Map of Infinity, he divided it into four parts and hid them in various locations. Paradox also created the Perplexahedron, where he established various security systems to house the final piece of the Map of Infinity.

After his experiment, Paradox learned the complete workings of space-time, allowing him to travel to any location in both space and time. He is also able to accelerate, slow down, or stop time at will, granting him seemingly limitless power, although he himself states that there are places he cannot go and things he cannot do, though these restrictions have not been explained. His powers are not limited to traveling within a single universe, as he can freely travel to other universes and the empty space between them. He also demonstrates the ability to rejuvenate a living being, but apparently, he is unable to perform this action with inanimate objects, having to bring them from the past. He is able to manipulate his personal time, making it appear as though he possesses superhuman speed (which, in a way, he does) from the perspective of others, but in reality, it is simply time manipulation, slowing down time around him while moving at a normal speed. He is also capable of teleporting people, objects, and even places (like the Forge of Creation) to a specific location and time instantly. He demonstrated that he controls and channels some of his powers through an old pocket watch. However, he cannot bring together different versions of himself in one place (like the Ben of the present and the Ben of the future) unless absolutely necessary.

In addition to his time-traveling abilities, he is also biologically immortal, requiring no sleep or food. He has also demonstrated the ability to revert Ben to his human form and presumably transform him into an alien as well.

Professor Paradox is a human being who, due to a failed experiment, became immortal and eternally young, retaining his appearance forever. Paradox appears to be a man in his forties or older, with short black hair. He typically wears a white shirt, a black tie, a brown coat, and over that, his white lab coat. He also wears green safety glasses, black trousers, and black shoes. It is unlikely that Paradox will change over time, as both his body and the equipment he was wearing at the time of the accident were rendered immune to the effects of aging. He lives an unforgettable experience that lasted approximately 1,000,000 years, but to him, it feels like a century.

His appearance changes drastically in Ben 10 Omniverse. He now has gray hair at the bottom, retains his green goggles, uses a cane, and his clothing has a steampunk style. He wears brown boots with lighter sections at the heel, brown knee pads with three dots, and black pants tucked into the boots. Instead of his robe, he wears a double-breasted vest and a belt with many pockets, a scarf around his neck, and a white coat with shoulder pads and pockets. His right arm is cyborg-like and contains his time-travel watch, while his other arm has a black glove with exposed fingers.

Professor Paradox was a scientist working at a military base in Los Soledad, where he developed the first theory of time travel in history using quartz crystals. The experiment failed, and the portal sucked the scientist out of the space-time stream, trapping him in non-existence for 100,000 years. For a time, he went mad, but then, bored, he began to study his situation, gaining absolute knowledge of space-time, as well as the ability to travel through time with his Chrono-Navigator, time manipulation, and immortality.

Species: Immortal Human
Age: +100,000 years (physical appearance of 30 to 45 years old, decided at the time of the accident)

Paradox is described as an extremely calm, free spirit. He tends to speak in very broad terms, like a stereotypical scientist, requiring extensive knowledge to fully understand him. In his first appearance, Ben tried to capture him (unsure whether he was a villain or not), but he escaped by teleporting several meters away. When Ben asked him how he did it, he replied, "It's called walking." He also often talks about events that, from the viewer's perspective, haven't yet happened, events that have become jumbled in his mind due to his frequent time travel. Because of his relaxed demeanor, it's difficult to tell if he's joking, like when he left Kevin a note saying that if his car came into contact with anything from 1976, it would explode—which was just a joke. Paradox only becomes worried or distressed when the risks to history or spacetime are very serious.