There's still no way to deal 80 DMG with 4 items. It is impossible. period.
Even if Mundo build ZERO additional Health he has 2000 at 18 resulting in 200 BotrK DMG before resistances. With LW Mundo would need like 400 Armor an still get 70 DMG. (STILL from blade alone)
Additionally you have your base AD, 4 Items and +15% DMG from Lord Dominiks (which btw.. also increases BotrKs DMG!)
Not even calculating masteries, where offense straight up outclassed the defense.
And I dont think Mundo build 



+ Bond of Stone and had a Support with
next to him!
Because a build similar to this HE WOULD NEED!
I dont even mind if you say, yo dealt no DMG, we all know Mundos ridiculous Heal especially when nobody cares about GWs and I play some ADCs so I know how pathetic your DMG feels if you're even slightly behind - but this 80 is just wrong, sry.