So how do you stop someone from charging you in the ring or in a streetfight?

A solid front push kick works best for me.

A solid front push kick works best for me.

You can go to the side really fast, or fake and go to the side. A sidekick or frontkick is good.

depends on what they leave open and what theyre trying to do, but just about any straight attack will do in the right situation. front push kick, front snap kick (to groin if street fight), a knee if theyre coming in low like a wrestler, or step in with an elbow to the face if coming in high... even a jab could work. also, you can dodge it, maybe throwing off their momentum or balance or just position.