If you're 50/50 on whether he did it fair and square, how can you be certain he would beat him fair and square without sufficient evidence?
Remove your bias. Even as a Mihawk-stan, if it's revealed that Shanks had to use some roundabout way to chain him because he was literally just that strong, there is a possibility that Loki could be stronger than both Mihawk and Shanks.
His bounty is 2.6 bil but if he was never chained for those years, he would have gained an even bigger bounty and could have been known as "Worlds Strongest Giant" or something.
One thing I am certain of is that he's stronger than Kaido. After luffy defeats Kaido and has become an Emperor and even stronger, Oda has to nerf Loki, he's a month away from recovering to baseline because of being weakened for so long. So whatever he does now he's literally weakened/ not at his best. And then he might learn how to use his ACOC better because of what Scopper said.
If we say Loki who killed harald is weaker than the Loki who set sail for 8 years, because that is the trend we have to follow with a character like Oden, who got stronger on the voyage, then even if it's only 10% stronger Loki would be stronger than when he killed harald.
And then we have to factor in his potential Zoan Hybrid form on top of all of this.
Shanks could have equal to or maybe more haki mass than Loki, but that doesn't necessitate that he's stronger than him overall. This is why it's interesting Oda put emphasis on the volume of haki someone has. It's similar to concepts we've already seen in JJK or Naruto etc.
First of all, 50-50 refers to Story Choice, meaning I'm not certain which Scenario Oda went with,
But Combat Wise? I have 0 Doubt that Shanks can beat Loki,
Secondly, I don't put Loki above Old Gen yet, neither Roger nor Garp nor WB nor Kaidou ... etc
Why? Because the whole point of Adv. CoC is that it makes "Lineage Factor" Advantage Obsolete,
Likes of Shanks & Roger & Xebec & Garp ... etc are Peak "Normal" Humans who have Adv. CoC,
It don't matter if you eat DF, make Contract with Imu, Scientifically Enhance yourself, be Born with Superior Body, wield Special Weapon ... etc
All of these make you Superior than Normal Humans, but Adv. CoC exists to Balance things, it removes that Gap,
You think Loki is Only One with Superior Body & more World Threatening Power than Shanks?
Same goes for WB, Blackbeard, Kaidou, Big Mom, Luffy, Sengoku, Admirals, Gorosei, Harald ... etc
But when Adv. CoC enters the Conversation, Lineage Factor/Science Advantage leaves the Room,
Threat to The World have No Cap, Oda will continue to Introduce more & more dangerous Characters,
And Yes, Loki seems to be Bigger Threat than Kaidou or WB imo, but in a 1v1 Duel? It's all about your Fighting Style & Adv. CoC,
Thirdly, for Loki vs Harald, the Fight is Separated into Two Parts,
1. Loki Hitting Harald repeatedly till He regained Consciousness
2. Loki Killing Harald after He stood still & accepted his fate
Hitting Harald isn't a Feat that makes me go: "Oh, Loki can beat Shanks", because even those Guards can Hit Harald, and so did Shanks/Gaban, Loki's Only Feat was that his Attacks could work on Harald, that was the focus & mystery of that Fight, not that Loki can tag Harald or land finishing blow if Harald stands still defenseless,
Just because Loki's Attacks can work on Harald, doesn't mean He beats any Character who can't,
Shanks & Mihawk Fight revolves around them not letting you land a single Hit, not take it with their body & hope your attack doesn't work on them, which means what your attack do is irrelevant, the question is, can you outperform them in close combat? And the Answer is No, because I have yet to see a Character who can,