It's debatable. There are many strong fictional characters, and it depends on various factors like powers, abilities, and the context of their stories.
I think Zeno would be a really tough opponent. Zeno has the power to erase entire universes, and a Goku and Goku Black fusion, despite being extremely powerful, would have a hard time against such a being with god - like powers.
Goku's ultimate form in the manga is Ultra Instinct. This state grants him enhanced combat abilities and reflexes. It's a breakthrough that showcases his potential and is a key factor in his toughest battles.
It's really hard to say. Goku has the power to destroy planets and reach incredible levels of strength with his Super Saiyan forms. However, Naruto has the power of the tailed beasts and his own sage mode which gives him a huge boost in power. And Sonic, while he may not have the raw power like the other two in terms of destruction, his speed is so great that he could potentially outmaneuver both of them. So it really depends on the situation and how the author writes it.
One key moment was when Chichi first declared her intention to marry Goku when they were kids. Another was when Goku finally agreed to marry her. Also, every time Goku returned home safely from a battle, the warm reunion with Chichi was a significant moment in their love story.
One important moment was when they first met. Bulma was looking for the Dragon Balls and Goku had one of them. It was the start of their long - journey together. Another moment was when Goku transformed into a Super Saiyan for the first time. Bulma was there to witness this amazing power and it changed her perspective on Goku's potential even more. Also, when they fought against Frieza together, with Bulma providing crucial information and Goku doing the fighting, it showed how well they worked as a team.
It's really hard to say. Ben at his strongest has access to some incredibly powerful alien forms. But Goku at his strongest can literally destroy universes. However, if Ben could transform into an alien with reality - warping powers, he might have a chance. But Goku's speed and combat experience are also very high. So it could go either way depending on the situation.
Definitely include Bardock's last stand. His heroic yet doomed battle is a crucial part of the Saiyan lore. It could be written in great detail, with Bardock using his full power against Frieza's forces.