Have you ever paid attention to the story archetype of a nemesis in a super hero movie? Have you noticed that they never started off evil but after constant ill mishaps in their lives, they are taken down a dark path. Todd Phillip's Joker, is a recent movie which takes you into a journey which you see the human before the evil begins.
Now those are extreme examples and fictional but nevertheless helps us understand evil. In our macro interactions of our daily lives, you may have gotten hurt, been taken advantage or been manipulated and you are left feeling like somehow they got away with it.
You may start to question why? Why did it happen to me, why am I left hurt whilst they are ok? This natural feeling may take you down the path of thinking if you act like them, then atleast you won't be hurt again. But remember hurt people, hurt people.
The islamic paradigm is that everything is a test and hence it's not what happens to us that matters but rather what we do after that really matters. It's really important to break the circle and not become the people that hurt you. They then have won twice over.
Protect your heart at all costs, setup boundaries, learn from your mistakes, chose company of people more wisely, are some of the things you can do so that your heart remains clean and you are still able to do good. That way you can be a source of benefit for this world and the hereafter.