Accelerated Development

Accelerated Growth Rate is the ability to raise ones skills and abilities at an extreme rate.

Overview
The user is able to grow stronger and faster through fighting or training, improving their natural abilities far faster than most characters in the series.

Saitama has reached unparalleled levels of strength, speed, and durability during his training regiment. According to Genos, Saitama himself cannot explain the secret behind his strength, and the cyborg believes that it shouldn't make him that strong with that level of training.

Garou's usage of this ability is at an incredible degree, as he quickly gets stronger with every fight he is in, being able to quickly adapt to his opponent's fighting styles. His usage of this ability is enhanced even further when he begins to transform into his half-monster state, going from struggling against Royal Ripper to being capable of defeating the monster in a single attack. During his fight with Orochi, Garou has shown to become faster the longer he fought, only being subdued when the Monster King decided to quickly knock him unconscious without giving him the chance to become further stronger.

When battling Superalloy Darkshine, an extremely powerful S-Class hero known for his remarkable strength and overwhelming durability, Garou initially could not even injure the hero and had difficulty keeping up with him. However; as their fight went on, noted by Darkshine himself, no matter how he was beaten up, the Hero Hunter constantly got stronger and faster, as well as being able to further improve his techniques even while fighting, allowing him to completely overwhelm the hero.

Trivia

 * Even though Garou's usage of this ability is similar to that of Metal Bat's Fighting Spirit, in his case however, Garou's boosts are permanent whereas Metal Bat's are only temporary.