Death Becomes Us
Anything I say about Thanos is based solely on what I've read ABOUT him and this miniseries, because that's my only previous exposure to the character.
It appears that Thanos is driven by purpose itself. He doesn't realize it, but he's always searching for a reason to kill, while telling himself that the killing is simply done in the name of his purpose. What we see here is his spiral of obsession with death itself as a concept, and he loves it. He is basically revealed as the Cain of Titan, the 'inventor' of 'murder' after it had faded from memory in the society he was born into.
I'm still confused as to why Death is hanging out on Titan, but her twisted 'relationship' with Thanos is becoming more clear and more interesting. It conflicts with the Death I've seen in Deadpool, but it goes along with Thanos' usual motivations. Death is seducing him with no apparent intention of actually returning the intimacy Thanos develops for her. It makes perfect sense with what he's known to do later, we see the seeds of it planted here. Thanos is in love with death, he craves the intimacy he never had from his mother, but Death seems only interested in Thanos as a killer. She makes an odd speech about love not being for the weak, rejecting Thanos' embrace because she can see it in him that he only seeks it for emotional comfort.
Maybe I'm enjoying this so much because in a strange way I can really sympathize with Thanos here, at least in terms of his unrequited love for the only person he could possibly love. Seeking comfort only to be rejected for attempting to use love for comfort.... The Thanos everyone seems to know appears to be in here, imho. It's his obsession with Death that causes him to become such a grandiose monster, because it seems that's what she's after.
In Conclusion: 5/5
I'm going into this as a mostly fresh new reader to the character. I've done some research, and in my admittedly limited experience this childhood seems spot on for Thanos becoming the man he is in Marvel today.