Reminder: The mastery Double-Edged Sword effectively lets everyone do 7.5% more damage
It's a tier 4 Ferocity mastery (so you can get it by putting 12 points in Ferocity) that almost everyone takes. If 2 champions in opposite teams have this mastery, they do 7.5% more damage to each other.
It's just one of so many masteries that increase damage, and is not even a keystone (Fervor gives 64 AD after 4 melee autos and TLD have 180 base damage and high scaling, etc).
And people wonder why damage is so high, why squishies (ADCs lul?) blow up quickly, and why tanks do unreasonable damage.