In my experience, the only real apology that matters is changed behavior.
This is something that I have been on both sides of. Apologies with written or spoken words, gifts, gestures, etc. are nice in the moment, but soon become meaningless if someones behavior is repeated.
I have always overreacted on him the past few months and he has
blocked me countless times and told me this is my "last chance".
By your own admission, you have a pattern of behavior that has been an issue in your relationship and clearly your partner has communicated that if things didn't change, that the relationship would be over for him. It also sounds like he's blocking you because he expects your pattern of behavior to be an issue even after the relationship is over and needs to set healthier boundaries for himself.
I had a similar situation with a woman I dated two years ago that was incredibly jealous and needy. She was never okay with me having female friends regardless of how platonic the friendships were and always considered my friends to be threats. I tried to reassure her ad nauseam how I didn't have feelings for any of them, but it always ended up with arguments. When I ended the relationship it was horrible and she did some pretty immature and petty things to spite me afterwards. She tried to paint this picture of herself as a victim on social media and was clearly just seeking validation from strangers to make her feel better at the time. She would post thirst trap videos of her proclaiming how sorry she was and how "she was letting me go", etc, etc. The stress of it all caused me to end up blocking her as well. I was so done and ready to move on. At the time, blocking her honestly felt like a huge weight had been lifted off my shoulders.
I wouldn't be surprised if your ex is feeling the same way as I did.
Unfortunately, there's not much you can do to change that except to respect his boundaries and try to move on. Showing him that you respect his decision by not overreacting and not trying to convince him that you should get back together, is also the best chance you have of getting him back as well.
I admit after a few months of not seeing my ex and after I had a chance to decompress I really did miss her. It was hard to not remember the good times we shared and we did have some amazing chemistry while it lasted, so I did reach back out to try and clear the air and extend an olive branch of sorts. Unfortunately after a few text exchanges and a bit of flirting, her old self came roaring back. She began grilling me about my friendships and took no responsibility for her behavior. That was all I needed to know that we weren't going to work out and I politely said goodbye and haven't spoken to her since.
Looking back though, I know that I was definitely entertaining the idea of us getting back together, because despite her behavior I truly felt that we did have a great connection and didn't want to let that go.
Obviously there's no guarantee that your ex will do the same, but if there's real love between the two of you and you had a genuine connection, then there's always a chance. So my best advice to you is to take this time to work on yourself and try to find healthier ways to deal with your issues that are causing you to overreact. You have to take it seriously too and you might even try consulting with a professional therapist, counselor, etc. It can't just be something you're doing with the hopes of getting him back either. It has to be something that you truly want for yourself if you expect to have any progress or change.
Your ex may never see the new and improved you, but you should at least take comfort in knowing that you truly learned from your mistakes and are serious about being a healthier partner in future relationships going forward.