-In your words, how would you define someone who is toxic?
In my mind, a toxic person is someone who is extremely manipulative and controlling. They take advantage of people who are generous and open, and resent those who are strong-minded and opinionated. They seem friendly enough when you first meet them, once you get closer to them, they try to exert control over you, push limits, and explode when you refuse or try to step back. They will go out of their way to spite you consistently, before switching back to being nice and normal.
-How do you deal with them?
In my opinion, toxic people are best kept at a distance. If you share a friendship group with them or have no choice in being physically close to them, it's really best to just not let them get too close/comfortable with you so they feel they can start their toxic behavior. It's much better to have one of these people to hate you, than to have them think they can treat you how they like. Sometimes, calmly telling them that saying/doing that is not okay can be effective, although it doesn't guarantee a reasonable response.
-Do you think being toxic is a case of nature or nurture?
Both. I don't think it's a case of upbringing as it is the friends they have. If they are surrounded by people who tell them "no" consistently, they will eventually adapt their behavior to friendly all the time, due to the need to be liked all humans have. If they find themselves constantly being rewarded (by having their friends/family forgiving them) for being nice, after being unkind/rude, they will get into the habit of flitting between the two behaviors, testing the limits of those around them. Additionally some cases such as autism, bipolar can effect this, but it's not an excuse, and shouldn't hinder your ability to put your foot down.
-Is it possible for someone to "reform" from being toxic?
Yes, if they the people around them tell them that it's not okay to act like that. They are fueled by forgiving, neutral people who want to avoid disputes at all costs. Once they realize this is no longer the case, they will feel pressured into being better behaved, as they still want to be liked by as many people as possible. However, when surrounded by very forgiving people, they will continue their toxic behavior, knowing that they can act like that because it will not merit any serious consequences.
idk why I'm asking I'm just interested as a psychology student I guess who's had experience with toxic people. What are your thoughts??