Real Talk: The Last Word is the only good gun in this game for PvP. The only other weapons that can be taken seriously competitively are the Mida Multi Tool for its strafe bonus and precision skill gap, and the No Land Beyond for its novelty.
No other gun lets you hipfire as well as The Last Word - Bungie recently lowered hipfire on all the other weapon archetypes, so this is all we have. Hipfire is important for mobility and of course shooting while airborne, which The Last Word also does better than even weapons with the Icarus perk.
Look at how cluttered Destiny's maps are; there are crates, railings, and other random shit blocking sightlines everywhere. And with how many Area of Effect abilities there are, staying still or moving slowly on the ground is a death sentence, especially when other players are blinking or skating towards you. The Last Word bypasses all of that and opens up the gameplay.
I've been playing Bungie games since Halo Combat Evolved and I still play Halo. It's amusing to me that Bungie effectively recreated the Halo CE Pistol in this game. It took 3 headshots and 5 bodyshots to kill a full health Spartan with the Halo CE Pistol, which is one bullet faster than The Last Word with Aggressive Ballistics (2 headshots and 4 body shots). The Halo CE Pistol however was very difficult to use - even pro players don't get the 3sk all the time. The Last Word has a smaller magazine so you have to be more precise, but it's way easier to use (especially since players move slower in this game). Some might feel like people are running around spamming a "broken gun" and getting easy kills, but these complaints were also said about the Halo CE Pistol, as if the principle of a small gun killing that fast is inherently wrong. But nobody who understands Halo would argue the Pistol broke the first game, so what's different for Destiny?
The only thing they need to do is make it take more skill to get its optimal kill time. Drop the training wheels and make it mean something to be good with this gun. That's why I and many others love it, especially people playing the game competitively. If people are salty about its ADS, then why doesn't Bungie implement a better crosshair and increase movement speed during Hipfire? Nobody really wants to ADS with it since ADS slows you down, but ADS is *still more accurate than Hipfire, even before the 2.1 changes. Besides, part of its appeal has always been the ability to do both.
I'm not going to say I'm not biased. Luke Smith has personally told me to stop talking about The Last Word because he knows how much it means to me. But for the reasons above, I feel strongly about it because there's just nothing else in the game like it. I tried to main Jewel of Osiris and Ace of Spades following 2.0, but normal Hand Cannons are easily overshadowed by Pulse Rifles and Scout Rifles. You have to be so much more precise with them, but then a Pulse Rifle can waltz right into their range and out-DPS them. And forget trying to kill a guy rushing with Shotgun if you have any other Hand Cannon out. The Last Word is the only one worth a damn.
Bungie sucks at nerfs. If they had their way, they would have doubled the kill time on the Halo CE Pistol 6 months after shipping it. The Last Word doesn't need a lot of range and it doesn't need a lot of stability, but as soon as they start messing with its TTK and accuracy, the gun stops being fun to use. Whether it is still broken or healthy for the game in the long run is on Bungie to decide, but whatever further changes they make I hope they consider its unique and very necessary role in the sandbox.