I’m almost certain Loki isn’t stronger than Harald. He will be but not right now. He probably let himself be killed by Loki or was weakened.
We saw Jarul get stabbed in Silhouette, not in full. We were told Loki stabbed Jarul in the head.
What is that's not a lie?
If Imu actually Domi Reversi'd Harald, the guy who fought Rocks to a draw, there's no way an older Jarul, pre-New-World Loki, and some Giant Guards are taking him down without hax.
So, how did Loki kill Domi Reversi Harald?
Domi Reversi makes the user grow drastically in size; I also believe you need CoC to overcome it (and strong CoC). Here's what I think went down:
-Jarul and Loki try to fight Harald but can't do anything, he's too strong. They're the only ones who can resist, because they both have CoC
-Giants are dying left and right, and Jarul realizes Harald will destroy Elbaph
-Jarul grabs Harald, and tells Loki to stab him
-Loki stabs through Harald's stomach/chest: the sword exits straight into Jarul's head and pierces his helmet.
-Harald reverts back to normal, and tells Loki something Oda offscreens, before he dies
-Since Harald shrinks back down, the sword cuts through his upper abdomen/shoulder, leaving the sword out of Harald, and stuck in Jarul's head
-Shanks and Gyaban show up to see Loki covered in Harald's blood surrounded by dead Giants
-Jarul has memory loss of the incident from the sword hitting his head