Iirc that was before he was taken over.
"Harald broke out due to Power of Love, and Loki killed him with Power of Love" (See how a Sanji fan said this btw?)
It's because Gaban says that you can stall the regen by overwhelming them with constant ACoC attacks, but he doesn't say you can outright kill them by doing this. So Yasheen decided to use it as an opportunity to push the agenda that you can only break out with PoL, even though Gaban literally tells his allies that you can only do it with ACoC and never mentions any other powerup.
Honestly the answer might not even be ACoC nor PoL. It's probably just the fruit given that Harald begged Loki to fight Ragnir and eat the fruit before it was too late.