In the runes there is crit damage runes and I wanna know how i could make myself do the most damage with 1 auto assuming it crits(wont need crit chance in runes because of the scaling AD vs Critical strike damage
Assuming you crit, each point of % critical damage adds 1% of your AD to your damage. When you critically strike, critical damage marks break even with flat attack damage marks at 42.6 AD and with scaling AD marks at 109 AD. Critical damage quintessences break even with flat AD quints at 50.4 AD and with scaling quints at 101 AD. When your champion has at least that much AD without runes their critical strikes will deal more damage if they have critical strike damage runes than if they had AD runes.
However, in practice critical damage runes are weaker than AD runes (or even armour penetration) for two reasons: you need a high critical chance to make them effective and they are useless against structures. The actual amount of damage you can expect to gain from a critical damage rune is (Current AD) * (Crit % Chance) * (Crit Damage % Bonus) / 10000. This is because it adds a small percent of your AD, but only a small percent of the time.
Critical Damage runes are useless early game because you won't have enough critical hit chance for them to pay off AND it's cheaper to invest in more attack damage early on. They can be useful as a late-game scaling tactic on ADCs because most ADCs reach over 200 AD and about 50% critical hit chance from their build. The problem is that they don't help you win until you have your first item or two, so it's possible for someone with better early-game runes to force you out of lane enough that you can't get the items you need for your runes to work.
crit damage runes are never worth it
