Its not easy though. Execution just looks easy until done yourself.
I remember back in SF when Viper had so many cancel strings and everyone thought they could do it..
HA! Leave him be. Hellfire aint easy to play.
I can do it, and I still feel he's overpowered.
Let me put it into perspective. Scorpion can get a 45% 1 bar combo, followed by an uninterruptible blockstring that does a further 18%. If scorpion lands a hit at the start of the match, he goes straight into his BnB and it's gonna be at least 38% regardless of what the hit was.
Now, let's say, the opponent tries to return after one rep of his 214 FBRC blockstring. He can now hit confirm a combo reset, and if the opponent doesn't break that combo he can end the round before they ever get to move again. That's being forced to use a breaker that was entirely built from nothing but taking damage. What's worse, if they wasted their 1 bar of meter at the start of the round, they won't be able to build enough meter for a breaker before they lose all their health.
Now, let's say in the second round, scorpion lands another combo. This time, the opponent turtles up and braces for the entire blockstring. Scorpion still has the opportunity to enforce a 50/50 after either of his FBRCs. Not only that, if he doesn't feel like taking risk, he can do the full blockstring and end it with an EX fireball using meter built entirely during the combo and blockstring, which leaves him at +8.
Now, from the average player's perspective, that blocked fireball is the signal to return. Scorpion can easily take advantage of this, because he is at +8. What happens next is obvious.
Now, against an expert, or someone who is equally familiar with hellfire, the logical thing to do is turtle up, because literally everything else is too risky. They are forced to eat huge amounts of chip damage after every combo, or even a teleport whiff punish. And again, every time this happens, Scorpion has all the options while the opponent has no good ones besides waste 2 bars of meter on a block breaker. Of course, this is speaking at the highest level. But even the best players I've met still attempt to take a risk after blocking an EX fireball, because it's their first chance to move since before they took over 60% damage.
All this, and not even considering his great long-range plays. Simply the threat of his unblockable can force the opponent to move (for some characters it forces them to simply jump forward), and that opens them up for teleport, among other things.
As for execution, anybody proficient in it will say that once it becomes muscle memory it's barely a problem at all.
No matter how I look at it, he has too many options.