The Goku Black Arc executed a lot of twists, dramatic moments, and ultimately provided a strong enemy at the time. Dragon Ball introduced Goku Black, an evil being taking the form of Goku to execute and destroy mortals with Saiyan Biology. Then, we see Zamasu develop his dark ideals, before revealing he is also working with Goku Black, and ultimately, is Goku Black from a different timeline. However, the ultimate culmination of their God complex and power turned to Fused Zamasu, a culmination of both Zamasus in different bodies. However, despite knowing fusion is a threat to the universe, not a lot is explained or known in Dragon Ball.