That's a tough one, especially since you are at this point and this child is 3.5 years old. Personally, I don't believe you "hate" this child. But probably more over you are mentally done with the early years of childhood and parenting in those years. I totally understand.
So what can you do? This I have wondered many times, but not because of a disliking toward my own, but more the blandness and monotony of early childhood parenting that makes everyday tasks and routines so painfully boring that you wish for it to end. But maybe not like end everything, but more like - can we just get to the point where we're all into our own things and you're in guidance mode more than total and complete slavery mode.
The most obvious answer is that time will normalize things and this will pass. But who wants to hear that?
In my earlier years as a parent, I realized that the general curiosity or engagement of children happens naturally, and without much need of deliberate interaction. But if I interacted, things would go more my way than whatever some may suggest. By that I mean, I can hand them a pile of little figures like those horrid LOL dolls, or whatever, and they will do what they do. But if I take a pile of them and re-tell some novel story with them, I can direct them into more engaging nonsensical activities that question and solve as the play time I share with them evolves. I can't say it was always fun, but in my own twisted way I did have some fun replaying the entire movie "predator" - yeah, the schwarzenegger one - to my toddlers with dolls and action figures. They got into it and eventually took off on their own with weird tales and what.
This is just an example, but what I am suggesting is that while this child is young, you may benefit from dismissing the normal conventions and just go nuts down the ill favored "f*ck it" road and just do the nonsensical without questioning what society expects or worrying about how you feel about any of it. You've heard from all over that it's not the child's fault, nor yours per say. Some are harder to deal with than others but if you are feeling like a stuck parent and the world is on fire, maybe the only sane solution is to change your world.
To be clear, I don't mean like - f this, I'm out - I mean change the scenery, the habits, food, practices, and see if you can slyly introduce means of wonder into this child through playful manipulation that doesn't turn it into some kind of me vs you thing, which kids seem to love to do. More like - invite them into things casually, but on their terms. Say something like - hey I'm going to build a tower out of legos. want to build with me? then just do it on your own and see if this child joins. Make things out of clay, in their presence and try to get them to join in... dull suggestions, I know, but I kind of don't want to admit that my own lurings of my own kids could well be seen as an act for CPS to look into. I went full on psycho and somehow my kids are a total joy now (not that they weren't) but in comparison to the average interests of kids, I have managed to build a foundation of bazaar fascinations, interests in literature, albeit typically not ones designed for kids of their age, and interests in movies and shows that ... let's just say wouldn't be played at a normal kid's sleepover.
I always treated work like it was the worst thing on earth. Sorry sweetie. I have to waste my life for a while doing awful things nobody should ever have to do. I would much rather build a lego tower with you or dissect this hideous play doh creature, but I have to do this or we have to decide which cardboard box we want to live in. From day one, really. I didn't do kid talk. I always spoke with sarcasm, or just more like a comically negative overtone to the insanity of the world around us, but in a light hearted way and not one of total depression and defeat. I believe it made them understand that I was never choosing to work over being with them, and that may well be why your younger one is behaving this way. You appear to not want to be around them, and they may well be giving you a taste of your own medicine as they see it.
But get psychological about it. Delight in the odd and the strange and just get dirty into things you wouldn't even care to do normally. It might be the effort you extend now, with total resolve, that makes this whole situation turn around rapidly instead of fighting such a difficult fight over a much longer span of time.
One day this child will probably be every bit as amazing as the other and you will feel a certain guilt from having these feelings once upon a time. But you will also probably not regret it because it was whatever it was.
Additional thoughts -
Your post is pretty abstract. It requires inferring your plight without any real clues to know to what extent your nightmare is. My wife has a relative who had a problem child from day one all the way up until he died of a drug overdose in his 30's. He was the very definition of utterly insane without legally actually being so. I don't know if you are dealing with a child like that, or if you are just at your wits end in an otherwise totally normal situation.
I don't know how interactive you are with this child. I don't know if you are following like a modern child rearing approach (like you know, no negative words, no screens, no sugar, etc) or if you are doing the exact opposite and hoping an ipad will get you out of another tantrum. It's all speculation.
But for me, the details aren't as important as the notion that life has taken you for a ride over the past 7+ years. You are spent. So my advise can be summarized by suggesting you adopt some of the things I did to keep myself from breaking apart when the excitement of life had to be redefined into dollhouses, horrible youtube videos, bad literature, and being surrounded by people who all seem to think raising a kid has to go by a certain standard that doesn't include weird things like atrocities, profanity, or whatever you know would get the soccer mom's blood boiling. I was, and still am, a father submerged in the concept that the world around us is practically a work of science fiction and we might as well go full throttle into the abyss or face a life doomed to the hellish cyclical routine of the so called american dream. It was the act of giving up that made me realize I was trying to do things according to a writ that I never agreed with. So I threw the writ out.
I wouldn't change anything I did, but even I have those moments where I realize I took it too far. Thankfully, never to the point of actual violence or fear. Just real life, from the perspective that there is no spoon.