Why does this toxic guy keep coming back if he says he cares about me?

Long story short I have an on and off relationship with somebody I've known for years he is extremely rude mean and loves to talk shit but in between that when it's just him and I it's like nothing else matters I know he's toxic red flag but I really do care about him and he admitted to me that he does care about me too one day we got into a huge argument because he's just an asshole he can't take anything serious and I told him to just leave me alone and get out of my life like why do you keep bothering me and coming back so I don't know if you blocked me but we haven't spoken in months genuinely missed him and I know he's going to end up coming back eventually but why does he do this why does he keep coming back even though he's just going to treat me like shit and I know it's because I respond but there is a connection with us there's no denying it he doesn't act like this with anyone else when it comes to relationships he's a very closed off person and private but with me it's different we clicked right away we felt an immediate spark between each other I don't want to lose him I just don't want him to be the way he is with me I don't know what to do I know the answer would be to just leave him alone but I really do care

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I used Google voice text so please ignore the lack or punctuation or misspelled words.
Why does this toxic guy keep coming back if he says he cares about me?
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