Why is Zamasu the stronger of the North/Supreme Kai's?

[Xeztin]

Does anyone else suspect he was being trained by someone above him, like a God of Destruction? I find it weird out of all the Kai's he was the only one with the hate for humanity or that he is the best fighter of his kind. If it's just a coincidence, I wonder how he got so strong if he doesn't deal with humanity? Maybe fighting other Kai's? Black himself could be the one that trained him, in the manga signs are hinted at Black being a God of Destruction himself, especially since Zamasu called him his companion.

[Lionel]

He's what Ginyu described as being a "mutant" -- i.e. someone with an abnormally high power level. The phenomenon of characters having such disproportionately high power inherently is something that's been going on since Yajirobe and Goku himself back in the original DB. Zamasu is likely just one of these mutants, except on the scale of Kaioshins instead of earthlings or aliens.

[Sonicjamareiz]

Well Starfire I always had this strange feeling that Goku Black might actually be the U10 hakaioshin reincarnated since he/she already dead in the future timeline.

EDIT: Zamasu has Gawasu's potara earing which has kaioshin status shouldn't the U10 hakaioshin still be alive?

[Sandubadear]

Well Zamasu was just a random Kaio from a random universe. Someone has to be the strongest. It could have been the East Kaio of Universe 8. How he got so strong could be various things, like why Freeza was the strongest person in the universe if he never trained. Mutant prodigies happen once a while, in anime.

[SpiritBombTriumphant]

He's a villain. The bad gods are always stronger than the good ones.

[Cipher]

I think it actually makes total sense that the most prodigal fighter among the Kaio/Kaioshin would also be the one with a hate-on for mankind. Zamasu has a lot wrapped up in the superiority granted by his species and position, as well as his warrior pride.

[Hellspawn28]

He is from another universe, so kais in his world are probably way above the ones in U7. It seems like U10 may have less powerful beings seeing that Zamasu was unfamiliar with Saiyans.