It's pretty difficult to build a 5e powergamed character without homebrew or playtest content. I've genuinely never seen a build I'd consider so wildly out of whack from the rest of the party, even concepts people have made, and even then, they require specific magic items.

I'd just give character targeted magic items to the weaker players to bring them to the powergamers par, while rewardinng them with socially interesting magic items then sharpen the teeth to my monsters a little.

True, but what encounter are you designing? If I'm allowing a powergamed character in there I plan for it. Intelligent and powerful creatures target them with just as many tricks up their sleeves. These powerful beings aren't alone, and their posse attacks the rest of the party. In my opinion, it is very doable. Though it might get boring always having a Kaiju fight while the rest of the party is doing normal party stuff. The games I have allowed powergaming, the powergamer has always been the first one bored with the campaign.