Excellent, thank you!
So, couple follow-up questions, and correct me if I got something wrong, please
"PainResistPerHit" - As in, "the zed gains an 'immunity charge' from getting hit". The zed will stagger when hit if the current value is below 100%, and the numbers you state in the vid are how much each hit adds to the current value on them. So, 2 hits on a dog would set him at 180%, third hit would "resist" - and that 180% would decay below 100% in 4 secs? Or is it the hit that goes over 100% (like it is for crit resist on character), so the second hit on a dog would already resist?
Are glancing blows, dot ticks etc giving PainResistPerHit?
Think of it as a gauge, like stamina, if it fills up (100%) and overflows (101%-300%) the AI is able to immediately hit their target right back as long as they are in range and aren't knocked down or rag-dolled, no matter how many times they are hit. Even without an animation.
In your example with a zombie dog, the first hit adds 90% and brings it to 90%, and assuming you are using melee, by the time your second hit connects, it'll deplete lets say 20% for the 1 second delay, so your second hit will add 90% to the remaining 70%, making it 160%, which means it can hit you right back now, once the first hit's pain animation ends. Because it is the second hit that caused it to exceed 100%. So you'll very likely be hit right back after your second hit.
It is also possible for a second attack to exceed 100%, lets say 110%, but by the time the AI's attack would connect, half a second later, they are now below 100% so their attack will miss you, even though there is a full attack animation. However, if you hit them during this attack animation, then it will now hit you as you just made it exceed 100% again.
There are many times when I'm playing and a zombie will attack after I've hit them, and they don't have pain animation as my hit exceeded 100%, but because it is barely over 100%, they attack misses due to depleting below 100% by the time it WOULD have connected.
This is also assuming a zombie doesn't shrug off the first hit, and attack immediately after (This is a new mechanic added in A21), as this attack ignores PainResistPerHit completely, even if below 100%, they'll hit you.
Glancing blows add the full amount of PainResistPerHit just like a full hit, and burning them with a molotov will max out their PainResistPerHit to 300%, and you'll have to wait a full 15 seconds before it is safe to melee them again. Damage from bleed and electrocution don't build up PainResistPerHit. However, traps like spikes and barbed wire do.
I hope I explained this clearly