I've NC'd for this although this post is really outing. I'll try not to drip feed without turning this into a novel so here goes.
I've got a child who's about 1,5 years old. Exhausting but an absolute joy to be around! 
I was seeing someone for several months, exclusive, commited, the whole shebang when I unexpectedly fell pregnant. We were shocked of course but he promised he'd be there for me and our child which was a relief. In short, he wasn't. He withdrew from then on. He'd go several weeks without replying to my messages, I'd see him even less, or he'd say he was dealing with a suicidal family member and couldn't possibly meet up which was understandable of course, I later found out he was on a night out with his mates instead. He's someone who on the surface seems like a lovely and harmless person but I did notice early on that he also had a deceitful, manipulative side to him. As in, he'd lie to my face about certain things even though he was aware I knew the truth? He'd even go as far as claiming I wasn't right in the head, that never happened, I don't know what you're talking about etc. I remember when I was about 6-7 months pregnant, I was fed up with always chasing him and trying to get him to join me for scans, classes etc. So I told him as such, as calmly as I could, and all he is intent on is making me feel like shite by saying things like, "oh, you know how I always said I loved you, that was all for a laugh, I never meant any of it" and so on. Next time I saw him, he would insist he never said it! That I was making stuff up etc when I wasn't. I can't even begin to explain how upsetting that was whenever he did this because there was no need to make me out as if I were mentally unstable or lying when I have no reason to lie about the shitty things he has said and done. Regardless of this, I wanted to, if nothing else, be able to co-parent with him for our child's sake so I turned a blind eye to this.
It was draining trying to deal with him especially when he'd try and manipulate every situation in his favour. He'd tell his parents, Paris is being difficult as usual but what he'd fail to mention is that I was being stroppy because he'd promised me he'd show up at a hospital appointment and then didn't show up at all. I got a text the next day saying how he got drunk instead and forgot all about it. Yet whenever I told him how that made me feel, I was accused of being difficult and making things hard for him. This is just one example of many. His behaviour continued even after our child was born. On average, I'd get one message every two weeks asking me how IT (his child) is doing.
When the little one was about five months old, things took a turn for the worse. We had a huge argument where I was quite vile and hurtful which is something I'm not proud of. I told him how his child really does have a piss poor excuse for a father. He retaliated by saying it's probably not even mine. I'm fully aware he only said this to be spiteful and to hurt me back after what I said to him. I told him if that's how he genuinely felt, by all means, buy a test, and let's get this sorted then. He never took me up on the offer. I have not heard from him or seen him since then. He has also blocked me on social media.
And if I'm being honest, I can't tell you what a relief it is not to have this man in mine or my child's life anymore. It wasn't just the manipulating and the lies. It was the always going out, getting drunk, wasting every night in a pub (pre lockdown, though he did go to mates houses and got drunk there during lockdown 
), the bags and bags of coke. 
saying how he'd give it all up but by the next day, he was back to his old habits. I'd be lying if I said I wasn't relieved my child doesn't have to be around that anymore.
If you've read this far, thank you. My question is, my closest friend claims my child will resent me once they are older for not "forcing" a relationship with their father. That my child needs to have a relationship with their father no matter how shite he might be because she feels my babe needs to figure these things out by themselves, as in they need to see with their own eyes what a twat their dad is. I disagree with her, I do not think it's healthy for a child to be put through that. And to be honest, after everything that has been said, there is very little left to say now. He's made it clear he has no interest in this child so why should I then force this relationship on the both of them? If I felt it was in my child's best interest, I'd swallow my pride and contact their father but I believe my baby is better off without him. However, I can't stop thinking about what my friend said, I'd hate for my child to resent me because I didn't try? Any advice or even a bollocking is fine with me, too. I just want what is best for my child.