There about 4-5 characters in brawl that had supers that where pretty much instant kills, also keep in mind that they can only kill 3 people, others can kill more than 3 but it takes more effort. Please don't complain about this, level 3 supers are supposed to be really powerful.
So far 3 out of 10 has them. All other reveals would have to have them and you can bet your butt they're not.
Anyways you won't even get a super lvl 3 in your face if you don't allow it.
The only one giving him that lvl 3 is you, because you let him punch you in the face enough times. So stop that. Then he won't ever get an instant KO on you.
Sweet tooths level 3 can get you 4 to 5 kills so it doesn't seem all that bad that heihachi has 3 guaranteed. It all depends on the skill of the playa.
I make it rain with Kudos