Separate a direct address (meaning when the speaker addresses someone else, be it by name or otherwise — in the example, the direct address is my darling) from the rest of the sentence with a commas or commas. This means that if the direct address is somewhere in the middle instead of the beginning or end of the sentence, you need commas on both sides of it, not just after it.
I opted to use an em-dash after back with you, but you could make the last bit a sentence fragment instead and use a period rather than an em-dash.
I have died many times, my darling, and I’ve always ended up back with you — a different version of you, maybe, but you all the same.
If you’re opposed to separating maybe out with commas on both sides (I don’t know why you would be, but some writers have weird aversions to the most reasonable things), you can change the word order like so: I have died many times, my darling, and I’ve always ended up back with you — maybe a different version of you, but you all the same. Notice that there’s still a comma before but.