Guessed by @drbunnig
This game was my everything for four years. I played it nearly everyday, sometimes all day. In the beginning it was just for funsies in all the local single-player modes, then I got really into For Glory mode where I really valued every win against an online stranger, then I became one of the best players in my local region, and then I travelled across the country to play in tournaments, meeting a bunch of people along the way. It was all really, really awesome. The community was super awesome too, and having those friendships for all of those years is probably what kept me sane this late into my 20's. It all came crashing down when Smash Ultimate came out, though. I don't know if it has any correlation with the game's differences, but soon enough all of the worst in people started coming out, and as I distanced myself more and more from the community, I realized most of those people were not friends at all.
Still, I do cherish the amazing memories this game gave me, and how exciting it felt to learn a platform fighter for the very first time. The slower pace of Smash 4 compared to the more recent games I've played in the genre still stands out to me as one of its best aspects - this game was far less about frantic movement and insane execution, and far more about just reading your opponent's moves. It felt much more mental than technical, and as much as I like to be technical, I think reads are the heartbeat of a fighting game. Or maybe it's just cause it's what I do best, and that helped me be good at Smash 4.