When two players are attacking another player, the player who lands the final blow does not actually get the kill; instead, the player who previously attacked them (within a 5 second window) gets the kill, no matter what. This is consistent across playerKillCount scoreboards and advancements alike.

Steps to Recreate:

1) In Multiplayer with at least 3 players (A, B, C), get Player C to low health by attacking.

2) Have Player A attack Player C, but then allow Player B to land the final blow.

3) Player A will receive credit for this kill, despite not being the most recent attacker.