The Diamonds are the strongest characters in Steven Universe. While initially all four had damaging, devastating powers, each would have a change of heart that left them with much more passive, restoring powers. Pink Diamond was the first, going so far as to change her very self and giving birth to our title character: Steven Universe.
She wasn’t the last though: Steven was able to change the other Diamonds’ minds, and leave them with a commitment to leaving the universe a better place. Vote Zircon!