Most unnecessary killing---Tracee.
Most unnecessary whacking----Adriana,without a doubt.What information of value did Adriana actually have ? When Tony asks Christopher if she told them about Ralphie,he acts almost as if she was there,helping with the dismemberment.It's clear when the Feds ask her about Ralphie,shortly after he disappeared,she's genuinely clueless to his whereabouts,as she is to the truth about her uncle Richie and Big Pussy.There has long been an ironclad rule in Cosa Nostra----the men don't involve any woman in their lives in their activities,nor do they divulge anything but peripheral details,at best with regard to ANY Cosa Nostra business.While there have been a few violators of this rule,they are far and few in-between,as this is definitely a "whackable" offense.This rule is in place to protect the women from the very thing that happened to Adriana,as well as(as ALWAYS),the organization itself.Imagine if the women were more involved,how many times they would've been targeted by investigators.The reason why they aren't---in real life----is because it's well known that they won't get anything of value out of them.

As unrealistic as that whole storyline was----no worse example than SAC Cubitoso screaming at Adriana :"you've been giving us s__t...I want you wired up"---SERIOUSLY ??? What were any of the guys they were targeting gonna say to,or even AROUND Adriana ???? ---at least the FBI was shown as being just as scummy and ruthless as any of the Mob guys on their best day,when it came to getting what they wanted.I loved it in the beginning,when Adriana hurled all over them !!!!

Sorry about the rant,and back to my original point----killing Adriana was a ridiculous over-reaction and totally uncalled for.She couldn't of hurt anyone in the organization on her best day.If the Feds would've tried to make a case on her information,they would've been laughed right out of any court !!!!