Explanation that even if you get a strong Z soul, you will not become strong unless you activate the link ability. There is a link ability description at the bottom right of the soul details. Both the soul and the character belong to multiple link groups, and if the link group of the soul and the character do not match, the link ability "Kamesen-ryu no Teach" will not be activated. For example, Kuririn Soul in the image is a link group of “Earthling” and “Kamesen-ryu”, so it becomes stronger by equipping characters belonging to Kamesen-ryu and Earthlings.
You can check the effect of link ability by mouse over.
Son Gohan: As a child, I belong to a group of people such as Earthlings, Z-Warriors, Saiyans, and Sons. Since there are earthlings, you can activate the Kamesen style teachings of Kuririn Soul.
You can easily check even in the lower right of the set screen. If the link ability item is in yellow, the link ability is activated. Please refer to the link page of soul and character on the following page. You can also search.
I didn't know this so I couldn't win the last Veriha