Even though I haven't done karate in decades, here is a demonstration of one my kicks. Just for the giggles.
*Disclaimer: Don't try at home, or anywhere. Don't kick reinforced cement like this (heck, don't kick anything/anyone for that matter... you'll hurt someone else or yourself. This is for Demonstration purposes only.)
How to end a man's career in <1 second. hehe!
Your traditional Karate forward sack-kick. Simple, yet effective!
Let's face it, your aggressor is almost-guaranteed to be a dude, and chances are, even if he can bench press an elephant, he didn't condition his sack (or eyes).
If you are closer, or pinned to the ground. Just use your hands to hit and/or crush the same area.
No need to "other arm, other arm, other arm" the guy
with a million-move technique that will fail every time. hehe!
Of course, such moves are barred from the MMA and Olympics (and any other sport-ized style.)
Karate doesn't sport-ize very well because it's not meant for gaining points, it's transitionally meant for self-defense.
The goal being: to make the guy stop, or become hospitalized as fast/direct/simple as possible.
To focus all your power/speed/strength, making every kick or punch count as if your life depends on it, because it does.