Last whisper items vs the armor penetration items

VS . The max penetration is 20 on the other three items. The penetration on LW items is 45% bonus armor.

For tanks, I think the lowest armor item you can buy is 50 armor? so in this case the LW item still gives you 25 bonus penetration at the very least, 50 if they build thornmail . (I am aware it is 45% so rounding it off to 50%)

It only costs 2700 full build, has a pretty decent passive. I like mortal reminder mainly compared to executioners calling but to continue... The other three items are way more expensive. They have their own perks and benefits but I still think LW isnt a bad third item to build, or an item to start.

Typically around mid game adc, ignoring the korean builds, Its not a bad idea to try, .

I would probably do it in this order though, . Correction: phantom dancer after boots, before last whisper

You do have some uncompleted items, but the BF sword gives you a good amount of the damage for the completed items, phantom dancer gives you 30% critical strike, reduced incoming damage, and 45 % attack speed, boots are boots, and last whisper gives 35 % bonus armor penetration. I would probably continue infinity edge after this point, but numbers wise, especially if the enemy team has a lot of tanks and if you get an advantage in game, its not a bad build to start off with.