Relationship with toxic people

I don't understand why I've been through this many toxic relationships in a couple of years. There have been 4 toxic people.

First was a friend I met three years ago, and this was my longest interaction with an abusive person. He seemed to be a nice person whom anyone who knew would say is a good person. The first time we were having a conversation, he said something like "I know about xyz stuff" then I asked "oh really?" and that made him mad and he looked at me with wide eyes. Not being able to understand that he is mad, I just continued the conversation. He left abruptly. Then two weeks later, I would call his name in a place and he would not listen, and instead walk with a fast pace to avoid me. I felt insulted and hurt. And decided to keep distance with him. But the very next day he would come to me and sit beside his leg touching mine. It felt good. I started feeling a bond with him. But then such things keep happening on a regular basis. Sometimes he would talk in a sarcastic tone, sometimes he wouldn't see my text for a month while still being active on the internet. Sometimes he would ask me for help at work, and when I sent him the work he would act as if he never needed it. I used to feel anxious in his presence. I might do something which could make him mad at me. I started apologizing, a lot. Whenever I felt he was mad, I would say sorry without knowing what I did. And then he would ask "Why are you apologizing? There was nothing wrong? I'm sorry that you feel that way." I didn't know what was happening. I couldn't understand what reality is and what isn't. Then one day came when he showered all the love he had on me and it felt like I'm in heaven. That was the first time for me to have feelings for someone. But that lasted for just a day. Things got downhill. He would drop signs and flirt with me. And when I confessed my feelings, he started calling me slurs. My heart was broken into a hundred pieces. It triggered an anxiety disorder. For a few days I couldn't understand what happened. With time by following basic self love advice and trying to forgive him so that I could move on with my life. But he won't stop hating me. He would follow me wherever I go just to remind me that I'm gay and hate me for it. That was the time I found out that he is a red flag. I got to know that, he in fact cannot stand being abandoned but at the same time abuses whoever he is with. After getting this "revelation" from the internet, I tried it. I made it appear that I was leaving him, and he almost started crying, saying something like "how can someone survive without oxygen?". Then he in an attempt to prevent me from leaving, started behaving like he is gay too. It was really strange. And because I won't stay with him anymore even if he is claiming to be gay, then came the threats to kill me, and then came the threats that he would kill himself. I told this story to some of my other friends and he would not believe me (as everyone thought he was a nice person). But anyways after sometime analyzing the situation, he decided that I was right about him. I've been in no contact with him from that time.

By this interaction I learnt a few terms/red flags that I need to look out for to identify a toxic person.

Some of them include: instant valuation and devaluation, gaslighting, passive aggression, love bombing.

Second was a girl, with whom I had a small convo in a group chat, where she was apparently flirting. Then as the convo continued, and another girl talked to me, she got jealous that she started dropping many signs in the group chat, and reacting immediately to my texts. I DMed her to talk, so that we could form a relationship, but she would reply to a text once, and disappear for half an hour, then reply again, and disappear for another hour, then disappear for a whole day, just to say a cold "bye". Why would someone give you so much attention in group chat and not in the DMs? Oh, another red flag! I replied with "ok bye" and blocked her. She texted on the group chat "mf", so I left the group chat too. After a few days she got so desperate that she put a photo of a person on her pfp (I can't trust her enough that it's hers. I told myself that I dodged a bullet. Turns out she texts many men all the time.

Third was a trans girl. The story is so similar to the second one. A small convo on a discord server, she seemed interested in me, but instantly changed her mood, swears and left the server. She joined after a few days, and started lovebombing me. It was so much that one person started making fun of it by sending gifs of dancing a female monkey on a shitposting channel. I didn't react much to her.

Fourth was a girl who claimed to be autistic, schizophrenic and "having some other things". There was no instant devaluation this time. She dropped some signs and flirted with me on the server. Most people active in the server know that and were teasing us for it a bit, as people usually do. I eventually was DMing her and it was good for a day. The next day she did drop the same signs to another male on the server. In fact two males. At first I thought she was just trying to make me a bit jealous, I reacted with a few sad emojis and gifs on the server. Other people got that I'm sad because of her acting that way, but then she doubled down, by keeping the conversation for about half an hour, and kept dropping the same hints again. I felt deeply hurt by that. I asked her in the DMs "if this is a joke, please stop I can't take this anymore", she asked "what did I do?". I had a flashback about that first person I talked about, how whenever confronted about what they did, they always played dumb, trying to gaslight and question myself. I was rethinking my judgement for a few seconds. I said "I thought you were trying to hurt me". She said she didn't understand. I said "you're acting like an abusive person who hurts people and then acts dumb". She said "you're being hurtful". I said "I can't trust you". Then she said "then don't lmao". Then she decided to take this to the server, saying "someone from this server is saying that I am "abusing him" for no reason". People started taking her side. Why would you talk about that private conversation on the server when it wasn't necessary? This reminds me of the second person I talked about earlier. I decided to block her.