I think I can beat all overstocked tanks.
And I can do so with no guilt, because it was my dad's tank, when I was like 12 years old. It was the tank that sparked my interest in SW aquaria, but it ended tragically (as you will understand in a moment.)
The tank was an 18g hex.
UGF powered by one powerhead; crushed coral substrate.
The residents:
2 domino damsels
1 tomato clown
1 yellow tang
1 panther grouper (small, of course)
1 snowflake moray (about 12-14" long)
There was at least one other fish in there too, but I can't remember what it was right now... I want to say a purple pseudochromis or something.
My dad's big regret was that he never got around to buying an anemone for the clownfish. (under a single 12" plant/aquarium fluorescent, of course)
I think you can guess how this experiment turned out.
Back then it was just one of those things, no internet info, just an LFS willing to sell whatever you pointed at when you walk in the door.
Somehow this experience translated into me starting my own 60g when I was about 17 and developed since then into my decently developed reef. But I look back on that tank and absolutely cringe when I think about it.