In the Dragon Ball series, the ter, Zenkai is primarily used to refer the Saiyan ability to experience a significant increase in power after recovering from near-fatal injuries. Talking about Saiyans, both Goku and Vegeta have experienced multiple Zenkais throughout their journeys in Dragonball especially during the earlier arcs of the series.
Goku :
Goku’s most notable Zenkais occurred during the Saiyan and Namek Sagas. His power increased significantly after recovering from injuries inflicted by Vegeta during their first battle on Earth. Later, on Namek, his Zenkai boosts helped him to eventually reach new power levels, aiding him in his battle against Frieza.
Vegeta :
Vegeta also experienced several Zenkais. Key instances include his recovery after his battle with Goku on Earth, which made him much stronger when he arrived on Namek. On Namek, he repeatedly used this ability by intentionally seeking near-fatal injuries to increase his power rapidly in the fight against Frieza and his forces.
Gohan :
Now coming to other Saiyans like Gohan faced zenkais less frequent, but he also benefits from Zenkai boosts, particularly during the battles on Namek and in the early stages of the Android Saga.
Other Saiyan characters like Future Trunks and Broly also have experienced Zenkais, but the series doesn’t provide an exact count and as the series progresses into later arcs like Dragon Ball Super, the concept of Zenkai becomes less emphasized, with the focus shifting to new transformations and training methods.
