So me and my friend were having a discussion, and he said that the mage/apc is the best way to take down a tank, and I'm saying that the ADC is the most capable of taking down tanks. Can you clear this up, and explain why as well?
it 100% depends on itemaztion on the side of the tank, adc, and mage.
Sustained damage is better at taking down tanks. It's even better if the sustained damage doesn't cost any mana. AD carries are more capable of taking down tanks. Their DPS at full build are some of the highest in the game.
Then there's AP Cho'Gath who can deal 1000+ true damage from 250 armor/mr tanks and screw them over, but even that by itself won't be enough to take down a full HP tank.
Can I have a few calculations please? He's being overly stubborn
There are a lot of mages that can fight tanks effectively. Part of it depends on the items the tank is building, where the mage is in their item build, if they have enough mana (or regen) to support the fight, etc. Mages generally have the range to fight a tank without getting engaged on themselves, meaning they do a lot of damage without taking any. That's pretty optimal.
If you're talking sheer speed in killing a tank, an ADC is probably going to do that job better than a mage, but it's a lot more dangerous because auto attack range of a typical ADC puts them in a place where the tank can hit them, or CC them for teammates to follow up.
Which TYPE of champ depends on how the tank builds, which will be the best way to soak up from your team. Some tanks never bother building MR and stack the high hell out of armor.
There are a few champs that are good at tearing tanks down, typically DoT or DPS mages that can abuse Liandries and ADCs or bruisers that can abuse BotRK
It really depends on the champion and their build. 
can absolutely dismantle a tank with his combination of DoT and %HP damage. AP 
uses true damage to shred tanks. To a lesser extent, 
with his damage amp and DoT can proc 
over and over and over again. 
ult is great for the same reason, especially if paired with 
and 
.
On the AD side, basically any marksman with an AS steroid and 
can take chunks out of a tanks health very quickly. 
is extra good at this, with her %HP true damage. 
(literally) eats tanks alive by stealing their resistances.
Traditionally, it's the job of the marksman to kill the tanks. But there are AP champions who can step up to the plate as well. Just don't try to burst down a tank, as bursting down 3/4s of a tank's health is often not as useful as just outright deleting a squishier enemy champion.
neither can really 1v1 common tank picks with equal gold. the best 1v1 counter to tanks are actually bruisers and melee carries, because tanks do essentially zero damage to targets with resistances but huge damage to squishies, while bruisers and melee carries typically are both tanky and have high damage.
depends on the tank really. If they build more armor than MR than the APC will destroy him. And vice versa. The APC usually has a lot of burst which means they can deal a massive amount of damage but it might not kill the tank. The ADC however, has sustained damage making him do heavy amounts of the same damage over a long period of time.
So yeah, in most cases the ADC will be the best tank buster.
