should you always build Last whisper on adc?
What if they only have a garen? also, Should you combo this with BOTRK for total health shred? thats what i usually do
3 Comments
if they have no/almost no armor i suggest getting a 
and if they are building a ton of hp(at least 2 hp tanks) you can get a bork
Yes. Even if they have 60 armor, that is still around 30% AD damage reduction. You need the LW to penetrate that 30%.
You definitely need an armour penetration item. Even if the enemy hasn't built any armour at all every champion has about 80 base armour at level 18. That's enough to reduce your damage by 45%. It's a little closer to 50% if they've got flat armour seals, and much more if they've got an actual armour item on top of that. Also, even if the enemy team doesn't have armour Baron Nashor and turrets have a lot of it.
That armour penetration item doesn't have to be Last Whisper, but LW is the cheapest and most general armour penetration item. If you can use the cooldown reduction, The Black Cleaver can also be a good choice. If the enemy literally hasn't built any armour you can get away with Youmuu's Ghostblade because the extra critical hit damage will make up for the reduced armour penetration. Either way by mid to late game you can increase your DPS more efficiently by penetrating enemy armour than increasing your base damage.