Demon King Meliodas has barely done anything yet, waiting a few more weeks would be the prudent thing to do.
I was honestly waiting to hear your opinion of him tbh, IMO stomping the sins in that fashion after the feats they just recently presented puts him pretty high in itself. Also people are dismissing the PC feat when its practically classified a space/time hex.
What's he's done so far is certainly very impressive, but in the end, it's just more scaling. I'd prefer more clear cut feats and statements before jumping to a conclusion regarding his power.