The complexity and originality of characters solely depends on their D (Drive) button.
While I can tell you who is the most easiest to use, every character is different.
They maybe easy to use but each of them can be dangerous depending on how broad you want to go through them.
Two easy characters to use are:
Ragna - Uppercut, wall containment, guard break extraordinaire
Jin - freeze opponent for maximum damage. Pretty easy to use IMO.
Just because I say easy does not mean they are not complicated as well. They are easy to pick up.
The rest require a bit of work and study to win:
Arakune - traps and containment
bang - technical, you get 12 needles to use for poison, web, or just throw.
carl - He’s good on his own but better if you control Nirvana properly. Sandwhich combos are dangerous. carl + you + nirvana = ownage if you opponent does not know to get out.
hakumen - You cannot do moves unless you have meter. His meter accumulates in time. really slow but damage he inflicts makes up for it i guess.
tager - Imagine the opponent covered in metal. Now imagine Zangief with a magnet on his hand. Pretty strong but pretty slow. All about proper use of D button (Magnetize)
litchi - Same thing as carl but faster. Control the stick.
Noel - fast like hell. D button is a series of different attacks. Imagine MvC2 Hayato’s b.lp series. She’s fast.
Rachel - traps and technical but fun to use. Top Tier when used right. Yes, you do have to micromanage.
Taokaka - annoying 2a’s, really fast. Low damage at times. Easy to pick up. Annoying voice at times. Start button combos with her. If you want the challenge.
v-13 - short and long range. Sometimes D button does all the work.
NeoRussell