I’ll consider not only simplicity of gameplan but how effective a character can be even when you just picked him up.
1 - Liu Kang: It is really easy to apply his pressure, to start his keepaway, to get in, to keep people out, to anti air, to jump in, to take your turn, to mix people up, to condition people... he has answers and options for every situation and to access most of them you only need to press F and 4. There are 4 tiers of Liu Kang: There is ninjakilla, then there are the high level Kangs, then you have the average KL Kangs and then the players that don’t know what they are doing. If look at any random Kang footage that is not Ninjakilla’s or maybe Rewind’s you’ll literally take hours to figure who is playing.
2 - Geras: high dmg, scrubby jump ins, throw loops, amazing mids, scrubby pokes, scrubby fatal blow all locked behind the execution of a 3-year-old. It takes 1 hour to pick this character up, hit his optimals and figure his neutral. The only reason he is behind Kang is bc for a Geras to really reach the summit of bullshit he needs to learn how to FB OS everything, and that takes a bit of skill.
3 - Erron Black: no matter where you are in the screen, this character plays the game for you. When in doubt, B2. When in doubt but from a far, F4. When in doubt, from a far, but feeling kinky, Slide. Did it work? Repeat! Did they block? D1D3D4D3D4D1D4D4D4D3! I strongly believe he doesn’t lose a single matchup bc there is not a single character in this game that can keep him from doing what he wants to do everywhere in the screen.
4 - Sub-Zero: nothing like being reminded why MKX was such a stressful game. The moment you give someone a 50/50, it doesn’t matter how good you are or how bad they are, you can guess wrong and lose. He wants to mix you and he has every tool he needs to enforce that in the easiest ways possible! Throw loops, half-screen overheads, low profiling D4, broken jump ins, 6 frames-masher’s-wet-dream D1 and teleports in the form of dashes. Also, if the Sub player has bad neutral he still has a slide to break it or a fast projectile-eating iceball that is only punishable when in point blank range. I also don’t think there is a single character in this game that beats both of his variations, and he takes 0 execution to hit multiple 50/50s into upper 40s a match.
5 - Sonya: her rings are basically very very slightly toned down version of deadshot’s vanilla projectile and up close she mixes you just as bad as he did in I2, but this time for 30-45%. If you have the neutral, you don’t really need much more than knowing how to do her rings and B1 mixups to be decent at high level. Zoning is easy with her and opening people up is easy with her. She also plays MKX imo.
6,7,8 in no particular order - Baraka, Kitana and Kung Lao: I think they are very easy to play but the thing that makes me put them here is a common aspect: all they need to do to apply their game on you is press up, forward and a button. It is that simple, and 90% of the cast can’t anti air them (100% in the Kitana case). According to REO’s anti air stats the highest level of players only anti-air 1 out of 5 jump ins, which means that 80% of the time you jump you’ll get a free mix. Baraka only needs 2 to kill, Kit and Lao need 3-4, but once you hit up in the D-pad the odds are in you favor.