Goku Black was a powerful fighter that ended up destroying many worlds in Future Trunks timeline. It was revealed that Goku Black was Zamasu and that he was the original Zamasu before using the super dragon balls to switch bodies with Goku to become Goku Black. This version of Zamasu was one of the more sadistic versions and was one of the stronger versions of himself.
Goku Black was sadistic in battle and would prefer to harm his opponents as much as he could in battle. With Goku's body, Black considered himself to be incredibly powerful and dangerous. Like his other counterparts, he considered himself to be supreme to the humans and mortals despite having taken possession of Goku's body. Black also enjoyed the sensation of physical pain in battle much like how he enjoys other people's pain. Goku Black does not like to be overwhelmed in battle such as how he was overwhelmed in battle by Vegeta and is impatient to things that do not go his way.