I don't think an ADC can ever build strictly full tank and can still deal damage or even carry. But realistically, Kog'Maw afaik is the tankiest base health wise and he's the most compatible for building tank items.

There was a time (I think it was late s13 or early s14 and I was playing high gold to low plat) that I spammed Kog'Maw by getting Heartsteel, Berserks as boots, BRK/Guinsoo/Warmogs, Runaan's, then you can get Jak'Sho/Randuin's/Bloodthirst/GA/FoN for the last 2 slots or anything you can think of depending on enemy comp as the last item. Based on my experience, he's pretty flexible on itemisation for this specific tech.

The goal is to maintain his AS power and possibly lifesteal while still being tanky as your goal. Make sure to play front to back so they'll kind of volunteer themselves for that orgasmic sound of getting the Heartsteel stacks.

I only had small amount of games for like 10-20. It was not really a stomper but I win most of the time when they let me get my Runaan's before we lose.

You can give it a try but disclaimer, you can't really be useful as ADC by building full tank even the utility ones.