Unpopular champions that should thrive in a tank meta
Sustained damage out the ass, zoning out the ass, the master of stalls and kiting.
Tank buster passive, main item is liandies, tons of aoe damage, two second stun for when tanks try to jump him, very good at kiting.
AP Kog is rapidly gaining in popularity and for good reason, but I figured I'd mention him.
3 seconds of invulnerability, aoe attacks, good at kiting.
Even if he gets dove, he's still useful when he dies.
Thrives in long teamfights, tanks can't protect the carry from his ult.
Lee is probably one of the best champs at deciding where and when his team wants to fight, yet he's seeing less play than ever.
Wave to their front line as you bypass them completely.
Tons of sustained damage, a lot of AOE, Liandries is core on him.
Can't remember the last time I saw an Ori, and with the decline of assassins and rise of tanks, this is the time to do it.
The Glass Cannon Tank. This guy steals their tank stats and steals their ad stats.
Can pretty much bypass all tanks. His damage comes out so fast and his engage range is pretty long.
Disregard frontline, acquire carry.
An insane amount of sustained damage, no tank will ever be able to kill him alone, kiting master, thrives in long fights.
Tons of sustained damage, no tank will be able to kill him alone, thrives in long fights, a lot of aoe, and increases the damage of all allies.
Main item is liandries, tons of aoe, good range, a lot of sustained damage and zoning ability.
Long range, great at kiting, true damage, a lot of aoe.
Max health aoe damage, teamwide snare, healing reduction, kites and zones very well.
Builds liandries, tons of sustained damage, huge power to decide when and where a fight is, kite master.
Makes everyone tankier and stronger, has a stun for peeling, reduces tank stats of enemy team, has a heal.
True damage, does a lot of damage regardless of what he's building, an aoe grab.
Sustained damage, catch out potential is huge, builds liandries, %health damage, execute.
Gives no fucks about your frontline, true damage, aoe permaslow, can peel for carry or straight dive theirs.
Bypass front line. AP malphite's burst is enough to kill any squishy regardless of any situation. Tank Malphite is tank Malphite.
Kite master, true damage, aoe, high catch out potential.
Bypass frontline, tons of burst and sustained damage, pretty tanky for an assassin.
Bypass front line, invulnerability aoe ult.
Buys liandries, stun locks everyone, large aoe.
Large aoe, a lot of burst and sustained damage, aoe %health, builds liandries, can lock down one champion while damage the rest.
There's probably more than what I've said, but you should get the point by now. Also, I used unpopular as a loose term, these are champions I don't see often. I don't look up their global stats because I don't really give a shit about their global stats.

Is not really a tank buster, but rather a slow tank melter. It can work with some poke mages that have the CC to make full effect of the item. But a tank can shrug a good amount of the damage, and as the APC your still vulnerable to engage from the tanks. Before taking Brand, Teemo, or what ever because they can build Liliandrie's Ask yourself whether you can shred the tanks quickly enough and can you evade the tanks engage?