That's a good question but probably not as that would cause quite the shit-show.
Now this is just my opinion:
Hardest would probably be Thunder God - Raiden, especially the way Goonie & Justin Wong play it as a lot of players who don't play the character the way he's supposed to be played & just abuse his most obvious tools. Arguably Mileena especially when you look at Akromaniac, he does some weird shit that not even other top Mileena players like Melbu, Damaja & Semiij do but the way Semiij plays Ethereal is very execution heavy too. A character I don't think is "difficult" but has a move that is difficult is Jacqui & Stanky Leg, if it weren't for Stanky Leg & even with all the buffs to the timing it's still incredibly hard to do 4U4, we'd have a lot more Jacqui players if it weren't for the stupid input.
Easiest? Pretty much any character that all you need to do is read a textbook to be good with.
Like there's like 200 Kitana players that still play the game who are "high level" yet all play EXACTLY the same yet have no knowledge actual high level play or fundamentals yet struggle against a basic Ninjutsu Scorpion player who actually has those skills. It's not just Kitana same thing can be said about Kung Lao, Tremor, Jason, Kenshi (Possessed), Goro, Johnny Cage & Triborg (especially Smoke). Just playing online or watching how MKX is like today really shows the bullshit that players today getaway with in that game in comparison to it's heyday.
