Wow, my internet's down so I missed this thread. I play a purely defensive game. It's my playstyle and it works for me, MKX or not I do better playing this way.
Here's my candidates for best defensive characters.
Blood God, has great space control with B1 and excellent footsies / poke game in general, great backdash, punishes with really high damage, and has multiple defensive set-ups. Quite simply possibly the best, most well rounded defensive character in the game.
Hellfire, possibly the character with the most comeback potential in the game, has a legit 6f poke unlike Quan, one combo + one correct read on the guessing game wins you the round, you can literally get 100% off doing only that with a few bars. His footsies are also super legit with 3 great pokes and D4 / Flame Aura, 14% throws with the Aura up, and a badass uppercut, and the ability to meterburn them + NjK for 9% restands with OTG exHellfire.
And of course, Quan, the character I decided to main. The other two variations have excellent defensive tools but no armor thus struggle to deal with pressure, Warlock has all those tools + some of the best armor (defensively) in the game at the cost of a bit of damage. B2 is one of the best space control tools in the entire game outside of Ninjutsu (which is similar but breaks armor), his backdash is top 3, he has a 6f poke for breaking pressure, hes just nice, more +frames on the D1 would be nice but meh can't have it all. You can use his dope projectile game and just zone/backdash all day while mixing pressure when its your turn, and then get big reversal damage of his armour if you end up cornering yourself as well as switching position.
Characters like Sub + Lao, nah son. They might have good defensive options, but they are offensive characters at the core and suffer for being played passive/reactively.