What elevates a highlight to career-defining? Factors like degree of difficulty, competitive stakes, and aesthetic value are all important, sure, but there are others to consider. The most important of which is: How conspicuously the highlight demonstrates the singular set of abilities possessed by the person making it. In other words, a real career-defining highlight is one which you cannot imagine any other player, anywhere on Earth, authoring in quite the same fashion.
Keep all of that in mind while you watch, hopefully for the seventh or eighth time, Giannis Antetokounmpo block an alley-oop at the rim to preserve a two-point lead in the final two minutes of Game 4 of the NBA Finals:
Who else can you imagine making exactly that play, under those exact conditions? I'd argue that nobody else in the league fits the bill, not because nobody else in the league is as big or as talented as Antetokounmpo, but because his entire development arc as a player was leading to this point. In the span of about three seconds, Antetokounmpo went from stepping up to provide some help defense on Devin Booker, getting caught in no man's land as a lob was tossed over his head, and recovering to meet Deandre Ayton at the rim to detonate what could have been a series-altering dunk. That journey was made possible by the mere fact that Giannis Antetokounmpo is Giannis Antetokounmpo. He made the play because he is long and tall and athletic, yes, but also because he is always switched on when he's on the floor, and plays the game with a level of instinct that few others can match. If LeBron James's NBA Finals block was a pure distillation of who he is as a player—the speed at which he closed, the instantaneous spatial analysis that allowed him to pin the ball just before it touched the backboard—so too was this block a short, authoritative story capturing everything about what makes Antetokounmpo who he is. He's the guy who just goes, very quickly, in a particular direction or to a particular spot on the floor, and then when he gets there he just does it, because his body allows him to.
There's a play from Antetokounmpo's rookie season, of which at the moment I can only find an extremely grainy GIF, but which exists much more vividly in my mind, during which Antetokounmpo completely died on a pick set for Kevin Durant, who gobbled up the space left by Antetokounmpo's defensive failure in a few steps and skied for a layup at the rim. But then here came Antetokounmpo, refusing to understand that the play was over, that he had been beaten, striding through the paint in a few huge strides of his own and flying in from behind Durant to spike the ball at its apex. I remember seeing that play, and thinking something along the lines of, "That's the thing he has that nobody else does." It was that ability to turn a losing position into a winning one through sheer belief and instinct, that hunter's spirit, that made me think way back then that Antetokounmpo was going to be special. I saw the hunter again last night, and he confirmed that, yes, he is special, and, no, there is nobody else like him.
The difference between that block from his rookie season and last night's block are the circumstances under which they occurred, which brings up another important question in determining the importance of any given highlight: What was on the other side of it? Consider a world in which Giannis Antetokounmpo had, I don't know, really bad diarrhea in the fourth quarter of last night's game and couldn't be on the floor for that possession. Imagine Devin Booker dribbling into the lane, seeing Bobby Portis step up to cut off his drive, and then throwing a one-handed, running lob over Portis's head and to the far side of the rim, where Deandre Ayton was there to catch the ball and emphatically dunk it. Imagine how great that play would have been! We'd all be sitting here today lauding it as an act of basketball genius, a moment of sublime playmaking that punctuated Booker's 42-point night and elevated him to another level of superstardom. That we are not currently doing that speaks to the true value of Antetokounmpo's block. It wasn't greatness overwhelming mediocrity, but meeting someone else's greatness, at the highest possible point, and slapping it down.