Many civilians have a twisted understanding of how the military operates. Honestly, it might be best not to correct them. Their minds would be collectively blown if they knew the magnitude of downtime and dumb things that happen to our nation's fighting men and women. But one commonly portrayed character: the drill sergeant (or drill instructor for the Marines).
Another misconception is that NCOs are constantly barking orders in our faces. In reality, this is pretty uncommon outside of training, but not impossible to find. The truth is, the threat of a knifehand gets old if it's constantly shoved in your face. When the quiet drill sergeant unsheathes theirs, however, things get actually terrifying. This applies in Basic Training and continues through the rest of your military career.
You'll never see it coming...
Loud NCOs can be heard from a mile away. You'll hear them chew out a private for having their hands in their pockets immediately before you face the same wrath.
The quiet ones? Oh no. They'll hide in the shadows and catch you in the middle of doing something stupid before they make their presence known.
They will crush your body and spirit
You can only do so many push ups before it's just a bit of light exercise. Iron Mikes to the woodline and back won't hurt after you build up your thigh strength. Even ass-chewings get dull once you learn to daydream through it. These are all go-to responses for the loud drill sergeants. The quiet ones, on the other hand, get a bit more creative.
Want to know how to break someone's spirit while also helping them on their upcoming PT test? Have them do planks while reading off the regulation, verbatim, that they just broke — complete with page turns. If they stumble, make them start from the top.
Their threats are more sincere
The loud drill sergeant also tends to stick to the same basic threats. Sure, they may say they're going to smoke you so hard that you're going to bleed out your ass, but they can only say that exact threat maybe twice before it becomes silly.
The quiet NCO? Oh, hell no. That guy might be serious when he says he's going to suck out your soul...
They choose their words very carefully
Speaking of things becoming silly, have you ever sat back and contemplated the exact nature of most of the threats loud drill sergeants employ? It's impossible to not burst out laughing sometimes while on the receiving end of an ass-chewing in which every other word is a lazily-placed expletive.
The NCO that understands that expletives are punctuation marks will be much more successful in instilling fear among the ranks.