Though he is the most concentrated opponent and doesn't show any emotions in combat, there are some weaknesses that you might want to know about them.

1.  During the battle against the Joker, Zaydon's mind was building up with rage as he was killing many innocent people, abusing Harley Quinn, and injured/ almost killed Batman (Bruce Wayne) and the rest of the bat family. He begins to turn into Super Saiyan 2 and killed him.

2.  Zaydon has a major obsession on seeking justice and kill/ injured every enemies which pleases him.

3.  Zaydon has a PTSD when he was fighting Female Majin Buu, Black Goku, Zamasu, Androids 17 & 18, and an Android known as Laila.