"Some are born great, some achieve greatness, and some have greatness thrust upon them."
― William Shakespeare
"I tell you this: though neither he nor they yet know it, he is the greatest of all the Jedi. Jacen Solo is the living Jedi dream. Even without the Force, he is more dangerous than you can possibly imagine"
― Vergere to Nom Anor on Jacen Solo (Star Wars Legends)
"Were it not for that tragedy, Ki Sui-sama could have become one of Zhao's Great Generals."
The user has a potential and capacity for growth and learning beyond that of a normal member of their species, allowing them to learn and develop in a shorter span of time than normal members of their species can and even learn things which are physiologically more difficult for said normal members of their species.
Even as a chilld, Kenpachi Zaraki's (Bleach) raw potential allowed him to kill hundreds of outlaws and defeat captain Retsu Unohana.
Frieza (Dragon Ball series) has almost incomparable potential. Not only was he born with power that most beings would only dream of, but when he trained for the first time in his life…
…he gained power comparable to gods within four months.
Majin Buu (Dragon Ball series), while already godly powerful, has immense potential for additional growth...
...after training for just a few hours, he lost all his fat & gained muscle and became significantly stronger.
Born a mutant, Broly (Dragon Ball Super) has an abnormally high potential, even for a Saiyan.
Hayato Kisaragi (Hundred)
Jacen Solo (Star Wars Legends)
Anakin Solo (Star Wars Legends) had amazing potential in raw Force power. Even as a child, the level of his potential was acknowledged by Jedi, Dark Jedi, and Sith alike, including Luke Skywalker and Darth Sidious.
As the son of two powerful and famous Force Users, and the grandson of the Chosen One, Ben Skywalker (Star Wars Legends) was immensely strong in the Force from the moment of his birth.
Kou Yoku of the Thunder (Kingdom) has a great deal of potential with his swordsmanship...
...which allowed him to fight Great General Tou, an extremely capable swordsman himself, just days after he killed his general.