Do you have a professional to talk to, sounds like a fair amount of, ‘unpacking’ could be done around these 2 relationships, ( if you can find something you can afford).
Red flags started with them getting mentally bizarre, you’re noticing, perhaps be more sure it’s not ok and respect yourself by imposing boundaries early on.
People change, don’t we?

It is difficult to see what's right in front of you sometimes in a relationship. I haven't got the greatest track record in that regard. It has improved incrementally throughout my adult life but I still don't trust my judgment. And I'm in my 60s now.

So you're certainly not alone.

For me part of the issue is how I was raised, both with respect to religious ideation and just garden variety romantic ideation. Both thought processes tend to put special relationships into a sort of special pleading environment that is supposed to operate by different rules. They encourage projection of one's needs and desires onto an idealized other who may be unworthy of them and in any case, being human, are unable to bear them. Hopefully you take your projections back before the relationship becomes damaged, toxic and/or dysfunctional. And hopefully they do too.

Another factor in play is that as people get older they tend to accumulate more scars / damage from past relationships and many don't fully resolve the scars of childhood and that becomes an increasingly urgent need and often there's an expectation that you should have a decisive role in rectifying whatever insecurities or hurts exist around that. Instead, of course, without meaning to, you just press buttons.

Special relationships (not just S.O. / spouse but children, siblings, etc) just tend to amplify what you already (don't) have. They don't fix anything. Mine succeed only to the extent I've got my own shit together. For me at least that involves feeling complete and content as I am, within myself, and not looking for anyone to "save" me from myself or my demons or whatever you want to call it, or to "complete" or even "complement" me. People are going to do whatever they are going to do, for whatever random reasons, and if you expect from them even the levels of loyalty and devotion you're willing to give, I just haven't ever had the experience of not being disappointed.

Mind you I've not been recently disappointed in some relationship-ending way, just in lots of little ways. And I recognize others feel the same way about me. There's this weird dance between accepting each other warts and all, and not taking it so far as to "settle" for a fundamentally unsatisfactory and unfixable relationship.

Sorry to hear that, V.

People are complex and relationships exponentially so. People and relationships change over time, too - and not always in the growth direction. The bad guys don't wear black hats to announce to the audience they are the bad guys!

I guess it really comes down to knowing your own boundaries, what you are willing to let be in your life. People will always test and push on them, but may your boundaries be solid, known and move them reluctantly, even then only rarely. The only behaviors you are obliged to cope with are your own!

All relationships are optional.

Wow.. So sorry to hear this... Um... You met him here? How long did you talk to him before meeting him? Is he a newer member or been here for awhile? Does he post often? Or stay in the background? These are some of the things I consider when evaluating someone I meet online... I'd be very interested in knowing who this is.. Please pm me his name...

I'm thinking this situation may exceed the collective wisdom of this group. Certainly, the advice you receive here has value. But if you keep attracting creeps and don't know it until it's too late you might benefit from some professional counseling. Maybe there's something you're doing or NOT doing that's contributing to this.

Through out your life, you will find yourself in contact with fools and idiots.
Its a constant job to keep them out of your life. They are like mice, they are cute for awhile, but
are a pain after awhile. Then they start to stink.
I make it a point, especially after Trump, to identify personality types quickly and act quietly.
There's no reason to go apeshit. Just stop contact.
I've had enough of personality problems.

I used to have that problem, but I only say used to because I don't really make friends anymore. I'm friendly and will talk to just about anyone, but I'm incredibly cautious with sharing too much about myself. I've lost count of the number of times that being too trusting has come back to bite me.

I'm afraid I don't have any advice, though, aside from doing what I do. I don't think it's necessarily healthy though. I do wish I had friends sometimes. It's just difficult.

Red flags aren't singular. Once you identify one, look back and you'll see the ones you missed, and just don't miss them agsin.

Lots and lots of people in this world are great. Lots also suck, you'll run into them and be exposed to them your whole life. Minimise time with the latter and maximise time with the former. Buck up, you'll get the hang of it sometime between 30 and 40. Unless you're a slow learner like me.

It's always possible there are more bad than good people in the world!
That aside, I seem to get taken advantage of...I can be manipulated, have trouble standing my ground, and maybe tagged as weak by sociopaths who are good at "culling the vulnerable from the herd."
I try to not make myself a target, but to remain open and accessible to 'good' people.
How's that working out? I'm practically a recluse for the time being, but plan to take another shot at a social life, soon.
So not great right now.
But I haven't given up and neither should you.

I tend to not expect perfection from people. I know this may not be a popular take on your situation, but if your friends are all turning on you, it could be you. I’m sorry, truth is, people are flawed and so maybe give your friends a chance to make it up to you or give them a Do Over occasionally. If this isn’t the case I hope you understand I’m speaking from my own experience. My moods can effect my outlook on not only people but everything in my life.

First of all, don't blame yourself for not being able to immediately identify the
red flags. Some people are really good at concealing their true natures until
after they've lured you in.
In many cases, it's not until after we've gotten to know someone that we start
to see the "signs". By then, we're usually invested and tend to be more tolerant
and forgiving of their lesser traits.
Time and experience are often the only ways we gain the knowledge to know
when someone we're dealing with is someone we need to get away from.

It took me YEARS to be able to cut certain people out of my life, and only after they'd nearly destroyed me.
I wish I'd learned how to do it earlier in my life. I might have saved myself a lot of
heartbreak, stress, and trips to the hospital.
The thing is, now I know. I know what to look out for, and I am very slow to trust.
It's one reason I'm grateful for the interaction I have with others on this site.
I can control how much of myself I'm willing to share with anyone.
I don't have to let anyone get "close" to do any damage.

You have choices to make. Things that only you can decide for yourself.
Feel free to ask for support and advice here.
There are many members who are wise and caring, and will give you the
most reasonable responses they can.
You'll be okay. Have faith in yourself. You're stronger than you know.

Some people present a better version of themselves early on then once they feel secure about where the the relationship is headed the facade begins to crumble and the asshole they always were begins to emerge. It's happened to me, it happened to you, it happens to many people.

It's part and parcel of the chances we take to have relationships. Try to identify these false people as soon as possible to minimize the damage, learn from the experience and move on.

This experience is not unique to you.

Little advice: Men, in general, SUCK. I may go ahead and switch teams if I ever have any extra time for a relationship.

Cut them loose. You don't need that. You are BETTER than that. As for what red flags to look out for, they vary from person to person, so you will make mistakes in the future. I personally just go with my gut about a person.