My problem with that is that I kinda didn't follow comebacks- I just listened mp3 files instead of looking at mv's- when i got to kpop so i actually have no idea
First one for Big Bang I properly followed as Alive. It was literally a comeback, there were scandals, long as hiatus and lot of talk of them almost disbanding before it. Then they came out with Still Alive as intro and Blue as title (let's forget the other two titles no body gives fuck about those awful songs), saying that they are Still Alive and that "the winter had passed and the spring has come" (which is pretty much what Bom's comeback-debut was about as well nice coincidence right there). There is no more impactful comeback than that one for me.