Yasuo-More than a 100% armor Pen

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That's not how it works dude. % Pen is multiplicative, and will therefore converge to 100%, but never exceed it. 100% is the asymptote. Flat Pen does stack additively.

Penetration in general will not put you over 100% either, but reduction could. This is evident in MPen builds where you have MPen marks, sorcs, and haunting to reduce a champion's MR to near 0. Building Abyssal (which reduces MR) can effectively bring your opponent's MR to negative values for your damage only.

It is possible to put someone at negative MR but it is difficult. Usually you require Ryze, Amumu or Fiddlesticks to do so

Tho keeping people at 0 MR is very possible

Actually, reduction happens before penetration. So you would have to have more reduction than their MR to actually get them below 0.

It's possible, but pretty difficult. If a Fiddlesticks with Abyssal Scepter and an Amumu with Wit's End were to double-team the same person, they'd reduce the target's MR up to 80 points.

Also, reduction works in the reverse order that penetration works, so % reduction applies after flat reduction. So it wouldn't work to stack it with things like Kayle's passive.

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Penetration in general will not put you over 100% either, but reduction could. This is evident in MPen builds where you have MPen marks, sorcs, and haunting to reduce a champion's MR to near 0. Building Abyssal (which reduces MR) can effectively bring your opponent's MR to negative values for your damage only.

Actually, this isn't entirely correct. In any case where you are causing an opponent's MR to drop to a negative value, it is negative for all magic damage. The reason for this is because of the order of application:

1. Flat reduction
2. Percentage reduction
3. Percentage penetration
4. Flat penetration

Reduction actually drops the target's MR, while penetration merely ignores it without changing it. Since reduction is applied first, if it's insufficient to bring the target to a negative value, the target will not break the 0 barrier. If it does drop the target below 0, it's applied to all magic damage for the duration of the effect.

Example 1:

• Fiddlesticks has the following sources of reduction/penetration:
• Greater Marks of Magic Penetration: 7.83 penetration
• Mastery - Devastating Strikes: 6% magic penetration
• Dread (Passive): Terrify and magic damage reduces target MR by 10 for 2.5 seconds
• Abyssal Scepter: Reduces magic resistance of enemies in range by 20
• Sorcerer's Shoes: 15 magic penetration
• Warwick has the following sources of reduction/penetration:
• Mastery - Devastating Strikes: 6% magic penetration
• Wit's End: Basic attacks increase your MR by 5 and reduce target's MR by 5 for 5 seconds, stacking up to 5 times
• Sona has the following sources of magic resistance:
• Base MR: 30
• Greater Glyphs of Magic Resist: 12.06

When Warwick and Fiddlesticks combo their ults on Sona, this is what happens:

• Warwick's uses Infinite Duress (5 hits)
• Each hit reduces Sona's MR by 5
• Warwick ignores 6% of her current MR with each hit
• Sona is at 5 MR when he has finished
• Sona is in the Abyssal Scepter's Aura: 20 magic reduction
• Sona's MR is now at -15. Any penetration is ineffective until her MR is back to positive
• Fiddlesticks uses Crowstorm.
• Dread is applied: 10 magic reduction
• Sona's MR is now at -25 for all incoming damage

Example 2:

• Fiddlesticks has the following sources of reduction/penetration:
• Greater Marks of Magic Penetration: 7.83 penetration
• Mastery - Devastating Strikes: 6% magic penetration
• Dread (Passive): Terrify and magic damage reduces target MR by 10 for 2.5 seconds
• Abyssal Scepter: Reduces magic resistance of enemies in range by 20
• Sorcerer's Shoes: 15 magic penetration
• Warwick has the following sources of reduction/penetration:
• Mastery - Devastating Strikes: 6% magic penetration
• Wit's End: Basic attacks increase your MR by 5 and reduce target's MR by 5 for 5 seconds, stacking up to 5 times
• Sona has the following sources of magic resistance:
• Base MR: 30
• Locket of the Iron Solari: 40

When Warwick and Fiddlesticks combo their ults on Sona, this is what happens:

• Warwick's uses Infinite Duress (5 hits)
• Each hit reduces Sona's MR by 5
• Infinite Duress ignores 6% of her current MR with each hit
• Sona is at 45 MR when he has finished
• Sona is in the Abyssal Scepter's Aura: 20 Magic reduction
• Sona's MR is now 25
• Fiddlesticks uses Crowstorm.
• Dread is applied: 10 magic reduction
• Sona's MR is now 15
• Crowstorm ignores 6% of Sona's MR (0.9) due to Devastating Strikes
• Crowstorm ignores 22.83 of (15 - 0.9) due to runes and equipment, not dropping below 0
• Fiddlesticks continues to damage Sona as if she had 0 magic resistance
• Warwick's attacks still ignore 6% of Sona's current MR
• Warwick continues to damage Sona as if she had 14.1 magic resistance

Wait... "continues?" Who are we kidding? We all know Sona died the second Warwick slapped her.

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I will explain

I am Garen, and I have built THE UNSTOPPABLE 9 THORNMAIL BUILD and have 1000 Armor

I have 91% Damage Reduction! Caitlyn just Critted Zilean for 2k and 1shotted him, She did the same against me and only did 180 damage (and died instantly because of the Thornmail effect)

Then Here comes Yasuo, With his Black Cleaver, Last Whisper, Masteries, Runes, and Ultimate

I believe Yasuo's ultimate applies first, so 900 of my armor being bonus Armor is reduced by 50% Placing me at 550 Armor Black Cleaver's 25% comes next and I'm down to 412 Last Whisper's 35% is next and I'm down to 267 Mastery 6% is next and I'm down to 250 Flat Penetration is next and I'm likely down to a flat ~200 Armor

With 2000 Actual HP, my 'effective HP' with 1000 armor was ~22,000 He has reduced my effective HP to ~6000

For comparison sake, let's say the person is not Yasuo 1000 armor after BC is 750, after LW is 487, Mastery is 457, Runes and Flat lets say 400 Effective HP to ~10000

{quoted}

I will explain

I am Garen, and I have built THE UNSTOPPABLE 9 THORNMAIL BUILD and have 1000 Armor

I have 91% Damage Reduction! Caitlyn just Critted Zilean for 2k and 1shotted him, She did the same against me and only did 180 damage (and died instantly because of the Thornmail effect)

Then Here comes Yasuo, With his Black Cleaver, Last Whisper, Masteries, Runes, and Ultimate

I believe Yasuo's ultimate applies first, so 900 of my armor being bonus Armor is reduced by 50% Placing me at 550 Armor Black Cleaver's 25% comes next and I'm down to 412 Last Whisper's 35% is next and I'm down to 267 Mastery 6% is next and I'm down to 250 Flat Penetration is next and I'm likely down to a flat ~200 Armor

With 2000 Actual HP, my 'effective HP' with 1000 armor was ~22,000 He has reduced my effective HP to ~6000

Incorrect First Cleaver takesoff 25% of all armor you now have 55.125 Armor and 694.875 Bonus Armor, total of 750. this applies to allies and minions and monsters attacks aswell. Then Yasuos ult breaks 50% of your bonus armor, so you now have 55.125 Armor and 347.4375 Bonus armor, total armor 402.5625 as far as yasuo's personal damage goes Last whisper 35% puts you at 261.665625 armor Mastery ArP 6% puts you to 245.9656875 armor Then Flat armor pen takes effect bringing you to probably around 215-225