Science and a benevolent nature have allowed thousands of different species to flourish beyond the capability of their environs to sustain the. The grand design has been thrown off kilter. If left on their own, this universe’s races will squander their riches and perish within a few centuries. The pendulum will swing from one extreme to the other. From an overabundance of life to no life whatsoever. My Mistress Death likes a constant and steady harvest, the balance must be maintained.
So even though Mistress Death doesn’t play a part in Avengers: Infinity War, his motivation is still somewhat inspired by the comics. His love for Mistress Death is also an example of something that works better in a comic book than it would on screen. Overpopulation is a much more concrete idea than a love for the physical embodiment of Death. Instead, in Avengers: Infinity War, we see the love he has for his daughter Gamora. Just like in the comics, where his love for Mistress Death is quite twisted, his love for Gamora is also very tragic. She’s the one person Thanos cares about, but not enough to forgo his delusional goal.