Only Loki's Supreme Haki was able to cause the death of Harald as Loki blew his upper torso apart but he was not revived in human form so higher covenants cannot be canceled out; They only result in total death. Imu stated that if they were to investigate like the Five Elders recommended it would result in the death of more knights and that performing the covenant inflicts a cost on Mu as well in chapter 1171. Checkout my patreon, full review for #OnePiece1176 among other manga like #boruto