I’ve seen a lot of people say that Padme’s death was Anakin’s breaking point/what pushed him past the point of no return but I honestly think that his breaking point was when Obi Wan said “you were my brother Anakin, I loved you.” Throughout their on screen relationship we see Anakin constantly striving for Obi Wan’s approval and love, whether he admits it or not. At the beginning of aotc Anakin literally tells Obi Wan that he sees him as a father figure. However, after Anakin’s mother dies there is a noticeable strain in relationship, which is probably due to Palpatine’s influence. Anyways, throughout the clone wars we constantly see Palpatine messing with Anakin’s perception of the Council and Obi Wan, making Anakin feel like he needs to prove himself in order to gain their trust/approval/love.
(Admittedly, Obi Wan did not really do a great job of making Anakin feel appreciated or loved either, especially with the whole Rako Hardeen thing. I think part of it is also that they have very different love languages too. Obi Wan seems to be more of an “acts of service” and “quality time” type of person while Anakin is a “words of affirmation” and “gift giving” type of person.)
I think at the end of the day, Anakin was looking for someone to give him some sort of paternal love and he needed some sort of verbal confirmation about it. Which is exactly what Palpatine gives him. Meanwhile, Anakin seems sort of resigned to his relationship with Obi Wan and he has a consistent belief that Obi Wan thinks the worst of him. This is briefly disputed in RotS when Obi Wan says he’s proud of Anakin and that Anakin is a great jedi, but I think his confrontation with Palpatine sort of shook that conversation from his mind. Furthermore, Anakin’s conversation with Mace Windu probably made Anakin feel like none of the council trusted him or took him seriously (which contradicts his earlier conversation with Obi Wan).
Also, trust goes both ways. Since the council had such a mistrust of Anakin, he felt like he couldn’t go to them with his issues, or like they were hiding information from him. But with Palpatine, he had to put his trust into the idea that he means something to Anakin and that he’ll be able to get him to fall. Palpatine doesn’t have to be coerced or found out by Anakin, he just straight up tells him that he’s a sith, which is an extreme risk to make. When presented with the option of entrusting the council (who does not extend the same trust to him) or Palpatine, the man who groomed him into feeling like he had no other options, he’s obviously going to pick Palpatine.
But here’s where Anakin’s breaking point comes in, after Anakin kills the Separatists, after he chokes Padme, after he kills the padawans, after he accepts Palpatine’s offer, after fighting Obi Wan and getting his limbs chopped off, after all that Obi Wan looks Anakin in the eyes and tells him that he was his brother, and he loved him. After all the heartache Anakin went through, after all the times he felt like he wasn’t enough for Obi Wan, after all the times he felt like he couldn’t confide in Obi Wan (and confided in Palpatine instead), after resigning himself to the idea that he’ll never have Obi Wan’s love or approval, that’s when Obi Wan reveals that he had it the entire time, that he cared for Anakin just as much as Anakin cared for him, that he had truly believed in Anakin and trusted him, that the distance between them had hurt Obi Wan too, and that Obi Wan was distraught to be opposing Anakin, that Obi Wan didn’t want to be Anakin’s enemy but Anakin hadn’t given him a choice because he thought he’d already known how Obi Wan felt. It must’ve broke Anakin to yearn for Obi Wan’s love for so long, and only realize he’d had it the whole time, and now he’ll never have it again.
All those times Anakin had believed Obi Wan disliked him, that he didn’t care for him, that he’d hated him for all the mistakes he made, and it’s only after he makes a choice he can’t come back from, only after he decides to return Obi Wan’s “hatred”, that realizes that it was never the case at all. That Anakin was the one who drew the line the in the sand, that maybe their relationship had been cracking, but Anakin was one who looked at those cracks and had decided that it wasn’t worth the effort to mend, that it was better to throw it away. All the while Obi Wan had looked at those cracks and loved Anakin anyways. And maybes that’s what makes him finally break, maybes that’s why he yells that he hates Obi Wan, because maybe if Anakin had known, he could’ve saved the relationship on his end, and maybe if he’d trusted Obi Wan, then maybe they could’ve saved Padme together, and defeated the sith. But Obi Wan never told him, and now the both of them were stuck with ruins of their relationship, always wondering about what could’ve been.