This depends on what you want to outspeed. You have two choices: jolly (+spe, -spA) or adamant (+atk,-spA).
Jolly hits 427 speed, allowing mega bee to outspeed base 80 scarfs.
Adamant gives bee more power, but only allows bee to hit 389 speed, underspeeding max speed crobat and base 70 or above scarfers like Tyantrum.
