IIRC the Mossad boys used the little 950 Beretta chambered in .22 short rimfire for the up close and personal executions they carried out on some of the kidnappers who killed those Israeli athletes at the Olympics in Germany. The .22 short has about the same power level as the .25 auto, but it's quieter and the soft lead bullet works better on brain tissue for the type of work the Mossad used it for. If you place the bullet properly so that it travels through the ear canal and into the brain even a .22 CB round will do the job.
I have seen my dad and my grandfather kill many cattle and hogs with a .22 short to the animals' foreheads at close up range. The cows always fell instantly like a ton of bricks from that one tiny bullet to the brain.
.22? I believe it would work as you say up front and personal. I had heard Mossad used the Beretta .25. I used to have one but you couldn't hit much with it at the range or anywhere else past 50 ft. Little bitty pocket gun.
Have a pair of Walther PPKs .380 too (thought James Bond would know what to carry) and just replaced them as carry gun with a Sig .40 229.