She could have the power of super - speed. Just like her father, she has trained hard and developed the ability to move at incredible speeds. This would make her a formidable opponent in battle as she can quickly dodge attacks and launch counter - attacks.
In a fanfic, Naruto might power up by having a spiritual awakening. He could connect with the spirits of past Hokages in a deeper way, gaining their knowledge and some of their power. This could enhance his existing jutsu and give him new abilities. Vegeta could power up if he were to face a near - death experience against Naruto. This could trigger a hidden potential within him, like a new type of Super Saiyan form that has unique abilities. He could also fuse with another Saiyan (if there were another Saiyan available in the fanfic's scenario) to create an even more powerful being.
He would likely have enhanced physical strength and speed, similar to Saiyans. Maybe he could fly like them too. His combat skills would be more brutal and direct, rather than the ninja - style he has in the original. He might also develop some sort of energy blast ability like Vegeta's Galick Gun.
In this fanfiction scenario, Naruto would inherit a host of Saiyan powers on top of his ninja skills. For starters, he would have the Saiyan's natural fighting instincts and the ability to quickly recover from injuries. His power level would constantly increase as he fought, similar to how Saiyans get stronger through battles. His existing jutsus like the Rasenshuriken could be infused with Saiyan energy, making it not only cut through opponents but also blast them with a powerful ki - like force. And with his Saiyan tail, if he had one, he might have an additional form or power that was unique to him, perhaps something that combined the power of the Great Ape form with his Nine - Tailed Fox form.
If Goku and Vegeta had a baby in fanfiction, its powers could be unique in various ways. Firstly, it could have a power that is related to the fusion dance but without the need to perform the actual dance. So, it could have a natural ability to access the power levels of a fused form. Secondly, it might have an ability to sense and manipulate energy in ways neither Goku nor Vegeta can. This could include being able to absorb different types of energy from the environment and convert it into ki for itself. Thirdly, due to the combination of their genes, it could have a power that is unlocked only during extreme emotional states, which are different from the typical Super Saiyan anger - perhaps a state of extreme determination or love.
In the fanfic, it could be that Bulma has fallen out of love with Vegeta. Maybe she has met someone else who seems more compatible with her. This new person could be more in tune with her technological interests or simply be more emotionally available. Or it could be that an event has occurred that has made Bulma see Vegeta in a different, less favorable light. For instance, if Vegeta made a decision during a battle that put their family at risk without consulting her, it could be a breaking point.
Android 18 might have a power - up where she can better regulate her infinite energy. This would make her attacks more consistent and powerful. Vegeta could power up by learning from his past battles with other strong opponents. He might unlock a hidden potential within himself that gives him a boost in speed and strength. Also, he could merge his Saiyan pride with a new fighting style inspired by his allies.
When facing a common enemy, Naruto's Nine - Tails chakra could be combined with Alucard's vampiric powers. For instance, the Nine - Tails' massive chakra could fuel Alucard's more energy - consuming abilities, such as his ability to summon a large number of familiars. In return, Alucard could use his knowledge of dark magic (if in the fanfiction) to help Naruto better control the Nine - Tails' chakra, maybe even creating a new form of chakra - powered attack that combines both of their unique natures. This combination would be extremely difficult for the enemy to counter, as it would be a blend of two very different and powerful power sources.
It would have a significant impact. For one, it would change the family dynamic. Trunks and Bulla would be greatly affected. Trunks might become more withdrawn or rebellious without his father around. Bulla would grow up in a different environment. The relationship between Goku and Vegeta would also change. Since they are rivals but also friends, Vegeta's break - up could make him more bitter or focused solely on training, which would in turn affect their friendly rivalry. Also, Bulma's role in the group might shift. She might become more independent and less involved with the Saiyan - related matters.
Perhaps Vegeta Jr could challenge Vegeta to a sparring match. Vegeta, being the proud warrior he is, would accept. During the fight, Vegeta Jr might display some new techniques he's developed, which could both surprise and intrigue Vegeta. And in the end, they could form a stronger bond as they realize they share the same values and goals as Saiyans.