No, itโs actually quite terrible in both regards, video game insta-kill knives notwithstanding. It either takes six good hits to the chest, all the while struggling with the target and creating one hell of a mess, or a hard to line up stab between the first vertebrae and the skull to sever the spinal column from the brain. The first isnโt that quiet or quick and the second is finicky at best. At that range, why not just dome them with a silenced .22lr pistol like the Welrod or a Ruger? Hell, a garrotte would be better than a knife, youโve still got a struggle but thereโs almost nothing the victim can do except gasp for air. My point is that knives are the meme weapon of stealth that should never be considered unless they are literally the ONLY THING you have on hand.
Ruger was founded in 1949 and as best I can find the lowest-caliber Welrod was chambered for .32 ACP, besides which a .22 would have the same issues as a knife as far as needing precision to kill instantly. You're exactly right that a knife is only silent if you get it right the first time, but A: it's a tool that's useful for things other than stealthy kills as well and thus a better use of a human's limited carrying capacity, and B: the SAS trained like madmen so that they would get it right the first time.
If you notice it, you can see that in the afterlife the Italian girl's pasta is severed right at the level of her neck. I bet the SAS girl went for the throat...
This image is from the Pixiv profile banner of the artist at the time of upload. It's also available in a regular Pixiv post from 2019 here, but in 1600x800 and with a watermark, so I opted to upload this version.
