'Human nature' is frequently thought to be not only negative, but permanently fixed:
"There will always be good people and evil people" and "You can't change human nature."

Others would disagree pointing out that

"'Human nature' is flexible and multifaceted, and that the behaviors of human beings are shaped by their social circumstances.
We are all capable of greed as well as generosity; which one gets expressed has more to do with the values of a society than with the inborn tendencies of the individual"

Revenge often (but not always) twists and perverts people into hateful, resentful, and bitter beings.

Denise Bulger – now called Fergus has campaigned (as is her right), unsuccessfully, for Thompson and Venables to be kept in prison for the rest of their lives and for that sentence be served in an adult jail.

In an interview with the News of the World she described herself as "paralysed with hatred" after she claimed she had tracked the adult Thompson down.

Interviewed on ITV's This Morning, when Phillip Schofield suggested there may have been other motivating factors behind the violence from the two 10-year-olds, Denise Fergus said she had never been able to believe that.
She said: "The two of them are pure evil in my eyes."

This is not a criricism of Denise Fergus - there but for grace - but it is a comment that 'human nature' is not always synonymous with hate.