People who can copy or steal abilities were looked upon as evil people.
It was not that their ability was evil, no ability is completely evil.
It's just how one uses it.
The people with those kinds of abilities often kill the one they steal an ability from, because they don't want trouble.
Because they don't want people to come chasing behind them.
But there are some people who kill their victims because they want to, they do it because they feel pleasure from it.
A devour-type ability is similar to copy and steal, it's just another level up.
It needs its victims to be devoured by them.
So, if this ability were to fall into the hands of someone psychotic, then it's the worst combination.
"I once heard that they had someone who could devour their enemies and extract their abilities….
An evil man, who would like to see his victims suffer as he devours them in the worst way they would want."