In chess, the Endgame is where you sacrafice pawns, or in this case, minor characters in order to get a powerful piece back. You can leave some pawns in battle while regaining power pieces. The pawns sacraficed were Peter, Stephen, Bucky, Drax, T'challa. Mantis, etc. While leaving behind two pawns: Nebula, and Bruce Banner. Normally I like to think of the Hulk as a Rook, but since he's completely useless at the moment, he's a pawn. Nebula's fairly worthless, so she's a pawn. Thanos is playing with all power pieces and one pawn: Gamora. He sacraficed his pawn in order to complete his queen equivilence: the gauntlet. Now he's playing with all power pieces, while the Avenger's have sacraficed their pawns in order to get their queen: Captain Marvel, who in turn will wage war on Thanos only to find that a pawn has made it across the board and turned into the Hulk, and fights side by side the original Avengers to get the soul stone, revive Tony, who probably dies, get their friends home, welcome new friends, and kill Thanos.
Sorry about the rambling. I'm not even sure if I got to the point.
