But to answer the question there is only one answer, KD. Imagine the pressure on him next year if for some reason GS cant get it done this year. Immense
The pressure is/will be on Lebron too, but for somewhat different reasons.
KD is chasing Lebron as the best player in the game. If the Warriors lose, that effectively ends that debate and if/when KD becomes the best in the game (when Lebron seriously declines or retires) he will never be seen as Lebron's equal, let alone the better player.
For Lebron, he's chasing ghosts. He wants to at least catch MJ as GOAT. If he loses, it effectively ends that discussion and probably seals his legacy behind Kareem and Magic as well.