I use this ithem s cuz it's really helping in late game and u vill do tons of dmg.
i use last whisper cuz it gives 40% armor pen + damage, banshee's veil gives good hp and mana + MR so u can't complain, some think that carries only need dmg to be good so many players who i have played with who plays carries only buy bloodthirster, black cleaver and infinity edge, they do like 300-400 dmg on each hits and shots but they have like 1500-1700 hp when they are full build so a mage could easy kill them with cc and spells, thats why i buy frozen mallet and banshee's veil cuz then i can stay in fights more longer.
Bloodthirster is a must on carrys, especially on vanye when her ulti gives her more dmg.
finally i go with Infinity edge who also is a must in carrys, givin 25% crit and 80 dmg, combin those ithems with the right character and play smart and right, you vill be one of dangerous players in the game.