How would you define an "evil person" ?

Indeed, as others have referenced, "Evil" is a label. There is no evil, just good and bad decision making. This itself is only relevant in a practical perspective according to the norm that society sits at.

An example is that Roman slaves (and Romans themselves, I believe? If memory serves...) killed their young children if they could not be taken care of or were, particularly as a harm to the overall family well being. (This among other possibilities). Is this evil? According to our current Norm - yes. Then? No. The norm was different and that was a conscious decision (in this instance) to save more lives than would be effected OR in a sense, compassionately killing something quickly that would otherwise have died slowly and painfully, yet inevitably and on a time scale considered "soon".

Our norm is much more refined and, in the relative scale, better. Our norm (at least in the Western culture) is set to a scale of what is and what isn't human. That is, better for the well being of the Human and Humanity as a whole to the point of every life being sacred. This is acceptable because we live in a society where, in the case of the Roman slave, a child can ultimately be taken care of one way or another.

So: normal is relative and the good and bad decisions are equally relative. Bad decisions are made according to the norm existing either in the society as a whole or, when divergent of this, in the mind of the person. This latter is an ultimate "truth" and is subject to many different inputs and interactions. Memories, cause and effect and relation thereof, chemical imbalances or neuro "disconnects"... all of these set the persons "norm" and is developed over the life as a result of nature and nurture.

"You mean Hitler's bad wiring allowed him to kill Jews?" - in part. But he was goal oriented and was, as a result of his development and thus resulting in his own norm which lead to a sharpened focus on a goal, likely committing necessary or even just minor offenses in order to accomplish a better "one world" goal.

I think most people are evil. It takes someone with honor and integrity to act in such a way that could indeed be detrimental to the self, simply because its the right thing to do. I am such a person and I dont consider myself corruptible.

A person who does something that I don't like.

Actually, I don't believe in evil. It's one of those things we made up to pigeonhole others into behaving in a certain way, rather than making their own choices and having their own consequences.

It's simple. An evil person is one who embraces evil traits willingly, despite knowing it is not good for anyone including themselves. You may not actually be evil, you just have evil desires. We all have them.

Someone who acts with intentions of hurting someone else. Or someone who acts without caring about what happens to other people involved.

A person without empathy or unable to feel the suffering of others.

I don't know an "evil person", I know only several people with an inadequacy of good.

I wouldn't label anyone as 'evil'