I hate GM Sub. Even though I play Cryo with the intention of transferring to GM once I've leveled up.
That said, I do not think GM is broken or anything of the sort. I feel like he is a solid character with defined strengths and weaknesses. He's definitely strong. But that's it.
The issue arises in his ability to automatically force most characters to play his game. Almost every fighting game I've played has had a character or two that operates like this. GM Sub MKX is its own little MKX ecosystem for many MU's. The most salt comes from GM Sub's polarizing factor. A bad MU vs GM is very bad, but the same can often be said for the reverse, when GM Sub has it bad, he has it very bad. I think if you ACCEPT that you must play Sub's game and stop raging at the fact you cannot, he becomes more manageable. Sun God, sadly, will always be painful vs GM Sub, but there have been several suggestions on what to do and how to do handle him. The biggest stumbling block is mindset. If you grind out the MU, really grind it out, and approach it with the understanding that you must play on his terms and wasting resources and life to the contrary isn't going to get you any where, then the MU becomes more manageable. Let him come to you. Don't lose.yourself in your offense. The SPLIT SECOND you start to chase a GM, you are going to pay for it. Keep that in mind.
Now, I'm a scrub and I'm full of scrubbiness, but oddly enough, what little experience I have had been like 80% GM Sub. I still get wrecked, but that's because I'm so trash I can lose aa game of MKX while playing SFIV. So take my opinions with a grain of salt, but GM Sub isn't op and he's not.unbeatable. He just forces his own little meta-game and you have to be conscious of that to succeed vs a well played one.. And of course some MU's don't have a universal, I WIN answer, so being.conscious of that and doing as well as you can, is all you can do.