Avengers: Infinity War was loosely inspired by The Infinity Gauntlet, but Thanos killing half the universe is only, well, half of the storyline.
Let’s not forget that at the end of Infinity War, Thanos’ Infinity Gauntlet, although damaged, was still intact, and the Infinity Stones appeared to still be functional, too, suggesting that he’s still an all-powerful, godlike being.
Eventually the surviving heroes had to triumph over him, and since we’ll (hopefully) see that happen in Avengers 4, then perhaps that makes Avengers: Infinity Gauntlet a worthy title candidate.
If the surviving MCU heroes can miraculously take the Gauntlet and Stones back from him, they might be able to undo his genocide.