I think I'd agree with this trade being Chia's worst. Sure, he got fleeced value-wise WAY worse in other trades. I mean, this doesn't even come *close* to the Hall for Larsson deal there. But even so, you could at least see what Chia was *trying* to do there. He desperately needed top-end D, he had McDavid, and so he felt that he could give up a top end forward to get it. That isn't a terrible thought process. The *execution* was terrible. He needed to get, say, a Seth Jones for his top tier forward, and instead got a Larsson. If he'd gotten a Seth Jones, the trade would have been generally fine.
The Manning trade, on the other hand, makes absolutely no sense whatsoever on any level. The only thing that would make it make sense is if he was deliberately trying to screw over the Oilers, because he figured he would be getting fired soon, so F those guys. Not only was there the obvious value mismatch, which would have been bad enough on its own, if not to the level of other deals. But this time, he got someone who wasn't even going to help you, had serious personal beef with your generational player and team captain, while simultaneously trading away said player's best friend on the team. The fact that Chia obtained an absolutely worthless player for a serviceable one combined with trading away a player from what already was a position of weakness served as the body of this **** sundae, the giant middle finger this one gave to McDavid was the cherry on top.