This is just my little thing on this issue. I'm just going to list this.

1. It stacks, meaning you can get 60% reduction for getting 2 of these, then you just slap on a Last Whisper and, tada! True damage.
2. 30% Reduction, meaning that when Malphite or Rammus builds 400+ armor, it shreads 120 armor ALONE.
3. Although I don't mind the it procs on Physical damage dealing abilites, the fact that it's 30% reduction is applied so fast on these abilities that the fact that it requires 6 stacks for the full effect means nothing.

I would love to see the passive become unique and the armor reduction to be nerfed a little bit. Also, perhaps the stacks could only have a chance to be applied to abilities, but a 100% chance to proc on auto attacks.

EDIT: Although nerfed on PBE, it still adds up to around 70% armor reduction, making tanks worthless when 1 ADC builds Last Whisper and Black Cleaver. Aren't tanks suppose to be a thing?

you're not reading it right... lol It caps out at 30% armor reduction atm in the PBE it caps at 25%.

The only part that stacks in its armor reduction is how many stacks you get per attack the Max is still 4 stacks and it doesn't care how many you have its still 7.5%/6.25% per stack.

1. No, actually, all that stacking it means is that you get 2 stacks per hit instead of 1. It still maxes at 30% shred (some people say there might be a bug where it does, but I've never seen it happen and I HAVE seen people stack Cleavers a few times now). Also, % effects always stack multiplicatively if they do not specifically say +%.
2. Last Whisper has always been this except without requiring 4 hits in a row.
3. It requires 4 stacks.
On the PBE, the nerf reduces the max shred to 25%.

If you're having trouble with Pen/Shred stacking, build health instead because pen/shred items have low AD values. It's called counter-building, and that's the job of a tank. Learn to play tanks properly.

Although I know what you mean. It still doesn't help that tanks that benefit from armor (Malphite and Rammus) can't build armor without it being worthless other than the bonus damage it gives.

So now there's a more easily visible counter to Armor-focused tanks. Big freaking deal.

Adding Blade of the Ruined King added a more viable counter to HP stacking tanks that works with AD and on-hit builders because of the increased sustain.

Yah it true black clever can be op like a wukong who almots can be atk and build 3 blackclever and ulti a team dealing almost true damage to all enemies. And have 750 hp 150 ad 30 cooldown reduction 45 amor reduction and 90% armor reduction. I think it really bad becose thornmail and armor got almot all reduce ex: thormail cost 200 gold more frozen malet gain 90 and no more 99 armor. This true damage is ok but it should be like armor more armor you got the least it good i think it total armor / (100 + total armor). Or like movement speed after 415 movement speed it onli 80% of the speed bonus and if go to 490 speed it onli 50% for more speed.

Thx riot.
sorry for the bad english.

I agree that it is OP. I had a match with an Amumu on my team recently who had 275 armor and got instantly melted by an enemy champ with 3 Black Cleavers.

Fiora just stacked 3 black cleavers....item diversity has surely been shot down...if this fiora was good it would have been even worse....I thought Riot wanted a variety of items that could be mixed and matched to suit any game not just stacking items. No amount of armor can withstand 3 black cleavers and another 2 on their adc.

Black cleavers is super OP right now, the stats alone are ridiculous but include the fact that it is stackable?.. Wtf was riot thinking here? Anyone lvl 5 league player can see this is OP just from looking at the stats.

Show me a level 5 League player who can outplay a cactus and I might take anything he says about balance seriously.

Yes, Black Cleaver should have been unique from the start. At the same time, people who are having trouble with Cleaver stacking should build health instead of armor if they want to tank it. Who cares if they deal 200 true damage per attack (most likely less than 1 attack per second) when you have a 5k lifebar?