It was the ml, the ml fckng broke the door and after that the mc had to move with him and then they agreed on a trial perod of living together. I dont remember why he broke it though, they were sleeping or smth, in other words they wouldnt open the door, and the door was of such a poor quality bcz the mc was so poor he lived in a shithole with the child, and then the ml just broke it. Anyway, good summary, in general the ogmc was not a good guy but the main point is the mls were not good guys either, the ruined the ogmc and then they expected him to off himself, thinking about this indifferently and now they have the nerve to approach the mc. The transmigrated mc is a sweetheart.
Well, the ML was not actually abusive in the present, he was just not a good person to the original ML and so it felt wierd for the MC and ML to get together as if the past had never happened. Nothing from the past was addressed. The MC did not have to feel guilty cause he had transmigrated, but others started liking him and never questioned how they had treated him before the main plot started without knowing he was a different person now, they just expected him to accept them despite the past and never thought like well it was shitty of me to drive him to the edge and even expecting him to off himself, he is actually a decent person now that i know him better. At least this is how i remember it.

this is going to be a long all over the place re-cap on my experience and what I remember. just in case you were going to search to read the novel basically mc is isekais into an omegaverse in the body of the "villain" omega who wants the ml so he messes with the og mc and he (og villain) went too far so the ml steps in and ruins the villains life bc the villains slept with the ml while he was in his rut and ml lets him go but makes him broke and alone that he has to go to the slums with the very little money he was given by ml villain gets depressed finds out he's pregnant and decides to "off" himself that's when Isekai mc gains consciousness realizes what story he is in and decides to keep the baby bc he used to be a orphan and never found interest in getting a relationship?(I think this was his explanation) and you know he does the thing where he avoids all main plot characters and make the life his own so as you see in the promo he has the kid and is working in this granny's restaurant which he's been working in since he found out he was pregnant and they've now become unspoken family (which I thought was sweet) her and the regular customers just dote on his child this is majority of what happens BUT I don't remember if its the ml2 or ml that finds first him but either way they find him and look in on the kid and something about ml2 is that hes the person who disrupted and destroyed villain mcs life on behalf of ml hes the mafia/gangster type that only has eyes for og mc and they try and get mc to act the way he used to so that they can find him guilty of trying to hurt the og mc again (I'm not really sure I remember this part correctly but it was something like that) they keep visiting the restaurant which annoys him but its great business for granny so she doesn't turn them away because paying customers but they never do anything openly disrespectful (I'm most likely telling this out of order but I've gotten this far so I need to finish) anyways the ml bumps into him a few times and wants to get to know his kid which mc is like ew no but he's also like i'll think about it because his kid does like the ml he's also like very rich and powerful and could take him by force which was also a factor in why he'd think about it so time "weeks" pass and he agrees to let him and the kid hang out and its fine but ml starts to overstep and tries to get close to mc (which is when I started disliking the story because 1- he had more chemistry with the second ml, 2- ml and the og mc are in this type of situationship where that cant be together yet because of something I forgot and the biggest problem 3- He ruined og Villain mc's life and wanted mc to off himself without him having too do it just so he could be with og mc who he's now neglecting) anyways they start getting acquainted with mc keeping him at arms length some time goes past idk what exactly happened but it was either maintenance on his apartment or someone broke his door leaving the mc and his 4/5 year old kid with nowhere to stay this gives the ml an opportunity to have them satay with him the kid likes it because his place is bigger than their apartment and obviously mc dislikes it but he has a kid and cant be out in these streets more time passes ml2 has been getting brownie points with og mc and ml and mc have been playing house ml sometimes take the kid to and from school and them picks up mc from work while this happens they start noticing each other in THAT way a ton of filler and will they wont they and they kiss then do IT because of heat/rut--- thats where I stopped reading because even though I knew it would happen eventually I still couldn't take it because although it wasn't the mc's life he ruined though it was mostly ml2's fault but he also helped he's still in the body of the person who's life he ruined which is weird to me that the ml would fall for him and it makes him seem wishy washy like all because the mc had his child he's suddenly hella attracted to him I was going to pick it back up eventually but I just cant anyways if you do read you might have a different opinion as me and its completed
that was my take thanks if you actually read all this ╮( ̄▽ ̄)╭