Board Thread:General Discussion/@comment-30406012-20170501174725/@comment-28010522-20170501181317

re: What if the reason Goku Black was so powerful

my 2 penny's worth. foremost, on what we do know,
 * Goku Black was Zamasu from an unaltered timeline
 * Zamasu is a Shinjin,
 * "born from magical fruits,"
 * "naturally born divine,"
 * "They possess godly powers,"
 * "The average Shinjin possesses special abilities that far surpass that of any sort of un-trained normal being."
 * as a Shinjin, they get to draw lottery, on who gets to become apprentice Supreme Deity,
 * and then, later, promoted (or take over) to the position as a Supreme Kai (or Supreme Deity).
 * Kais and Supreme Kais are not as strong as a God of Destruction, or Gods of Destruction

Goku on the other hand is a mortal, from the Saiyan race, which was able to reach the god-like but is still not a God (as of the current anime arc goes) (even though Goku has died multiple times, and has even reached the Angel status). that was the closest or highest Goku ever reaches, an Angel status.
 * Whis, who is an Angel, is described to have godly Ki, but Angels like Whis are not Gods, like Beerus. however, Angels like Whis can subdue God of Destructlon like Beerus from misbehaving.