A tank that counters sustained damage?

Go ahead and post suggestions on how not to make this an unfair concept. What if there was a "tank" specifically created to counter the common weakness of all tanks; sustained damage and focus fire, where their biggest point is not specifically to CC, but to draw attention to themselves as almost a raid boss

Strength in teamfights would probably be tailored to his ideals He wouldn't want to be ignored, so he'd probably have abilities to get himself into the enemy team, and then slowly begin to start CCing people unless he is damaged heavily, which would cause him to shift to a defensive stance that damages enemies the more they attack him.

Ramping damage reduction and %health regeneration the longer a battle goes, meaning if the whole team doesn't focus fire quickly enough, killing him becomes a minute long ordeal

Broken, I know. But with all this damage flying around, I want to see a champion whose purpose as a tank isn't flying into the backline and blowing up the ADC ( like what the heck is with that) , a tank that thrives on being the focus of the enemy team, with the tools to get their attention. He can't kill you unless you attack him. The enemy team will have to maintain a balance of damaging him enough not to allow him to start CCing, but not enough that he starts significantly damaging the team, with killing him only really being an option if he is caught out and immediately focus fired before he has a chance to ramp up, or if his team is killed and he is alone (it'd probably take about a minute at that point, so they may as well give up there) Long skirmishes would only work in his favor, as enemies start not being able to damage him enough to stop his CC train.

It's probably pointless to try to 1v1 him as any champ besides maybe vayne or fiora

How can we keep this overpowered concept from being terrible to play against?