My ex hates my guts.
It's normal, sure, but where does it come from? Why do they suddenly, or even gradually, go from loving you to bits, to hating the very thought of you? What causes this change that hurts us so deeply?
It's quite simple actually: they are still attached to you on some level, and they are suffering because they are subconsciously trying to deny it. They are trying to "convince" themselves that they do not love you in any way, thinking that this is how they are supposed to move on, and you become the "cause" of that suffering. The longer they deny it, the more the suffering grows, and likewise, the hatred and resentment toward the other person grows too. They begin to display negative emotions of varying degrees, from passive aggressiveness, to harsh remarks and snickering behind your back. If you reach out to them, they seem cold and rude, like you're irritating them and they couldn't be bothered with your presence. But these are all emotional responses that come from their deep denial of their true feelings towards you. They want you, they desire you, but they are convincing themselves that they don't. Even friends and family are perhaps trying to convince them that things "just weren't meant to be".
And there is only one reason why they deny these feelings: fear. They are afraid that if they accept it, they will lose their identity. They are afraid to accept it, because by admitting it, they're admitting that they were wrong all this time. They are hurt and they've associated too much pain to the thought of accepting their feelings for you or the situation. "People will do more to avoid pain than they will to gain pleasure."
But what does this mean? Does this mean that you go and beg for them back, or try to convince them that they have feelings for you? No! Because doing so will only reinforce their belief; because by doing so, you are revealing to them the truth which they'd rather not hear. The only thing you can do, is nothing. Nothing at all, except carrying on with your life. Why? Because it is them and only them who can consciously decide whether they will accept things or not, and end the suffering. They need to realise their feelings for you on their own, and nobody in the world can rush them.
Does this mean they'll one day come back? Possibly, but I wouldn't wait on them. Why? Because it could take years before they decide to face the truth. Do they truly hate you? No, they don't. They do love you, even if they don't realise it, but they're protecting themselves, and most of the time bullshitting themselves, but few people realise that its easier to live with love than to live with hate.
Do they ever move on? Yes, once they have truly accepted how they feel, and accepted the fact that they might never be with you ever again. Acceptance is the first step to letting go.
So how do you tell if your ex has truly moved on? Well, that's also simple: They are completely indifferent. People that have let go of their attachment, accepted their feelings and the situation and have truly moved on, don't hate. They don't swear or curse at you or call you names. They are civil, and again, indifferent to you or your life. Even to the point where they can be in the same room as you while your new partner can't keep their hands off you, and be unaffected emotionally. Sure, they still love you, but it no longer affects their lives. And if they still had unresolved feelings towards said ex, they'd have left the room by that point, or made a scene.
I mean, think about it… Why would they, or anyone invest all that time and energy into hating you or showing any emotional reaction to you if they didn’t care at least a little bit deep down? If a driver cuts you off on the highway, you are angry at him, yes? But only for that moment. You’re unattached to the situation, you get over it and move on with your life, but if you became attached to it and cared about what the driver did to you, you’d be talking about it weeks after it happened. Maybe even starting up some movement against reckless driving.
All the best!