Yes you're right. Striking the vital spots can end a fight easily. However, vital spots, including groin area, are small and are surprisingly not easy targets.
Most people, who are unfamiliar with boxing, tend to punch other people in the chest area or cheek area. That's because those are big targets.
The KO area is actually at the lower left corner or lower right corner of your jaw. Use the hard bottom part of your palm, and strike firmly but lightly at the lower right corner of your jaw. You'll feel a slight jarring sensation all the way up to your brain. If that was an average punch instead, it would be a KO blow. That's why in boxing stance, the back fist should be raised high enough to protect that jaw area.
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The black guy on the right is how most sinkies and untrained boxers stand, with both hands lowered, and the jaw unprotected. It's an open invitation for a KO shot at the jaw.
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Another negative example is the common TKD fighting stance, with both hands lowered to the chest level. It happens because of bad training habits, or fatigue leading to standing naturally in a lazy method, which is a sign of bad regular training. A number of TKD sparring ends with one side getting kicked in the head. TKD sparrers usually aren't worried about getting punched because both parties are equally unfamiliar with proper boxing and punching techniques. Their sparring opponent will usually step back to launch a kick, or simply punch them in the chest like an beginner.
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