Goku Black was as strong as suppressed SSJ2 Goku when they first fought, in his base. However, Goku Black had the same body as Goku’s body in the main timeline. Since they only switched minds, Black should not have any kaioshin magic in him, and Zamasu should not have been accustomed to his body yet. So why is it that base Black was so strong relative to Goku (no god ki being used, no SSJ3 or Kaioken being used, suppressed)?
Black gets large zenkais instantly after being punched a few times without healing, while Goku has to be beaten to near death and then fully heal. Does it have to do with the time ring making his body heal faster?
Goku Black shouldn’t be stronger than calm Goku in the second and third fights (angry Goku pushed Black back just like Vegeta did). They have the same body, so the only difference is fighting styles and techniques.
Why is Black so durable? He took a point blank Galick Gun from the so called Super Trunks (some sort of cross between SSJ2 and a false SSJB), but Trunks was stronger than angry Goku in that form.