Who do you think is the most annoying character to go up against? Not necessarily in terms of difficulty, but just as a nuisance who are cheap, obnoxious, or pestering to take out?
Loki, Bullseye (2*), and true healers I think
Cage with his passive shield that slows battle to a crawl. Especially if he is paired with a someone that can one shot you, and you need to finish before they get AP for their skill (And even if you deny them color it’s only a matter of time before they get cascade that will fill their AP to full).
Boosted Juggernaught. Personally any event that has boosted Juggs means I skip it as I hate every other turn Headbutt. Balance Of Power versus is different as o can just skip him.
Loki is most annoying for me. His illusion power takes so long to resolve, and he spams it every other turn
During pve, boosted juggs with goons feeding reds.
During PvP, I dislike seeing sentry because the ai seems to play him like a suicidal maniac.
Daken in addition to those mentioned (I actually don’t mind 2 star bullseye, I use him so the ways around him aren’t too bad)
a power that costs 5 in addition to an animation every time you match 1 of the 6 colors in game is fairly annoying.
haaaate OBW. haaaaate.
Johnny Storm - Human Torch, or Dr. Doom. Doom seems to just murder you from out of nowhere.
raisinbman. Hands down. 
All of the damned Dark Avengers. I’m sick of fighting roided out versions of these Aholes every single PvE. Retire these f-ers and give us something new, devs! 
special shout out to thugs; spammy 4 cost, 3 turn CD, can’t reach? haha eat sh*t, here’s 3.5k damage.
little bastards
Daken. Every other turn he launches his crotch into my face. Don’t be that guy Daken. Rags is a close second with his constant spamming.
Loki --» steals and upsets me with that Illusions. But still or just because of that I have him at 166 
Professor X. More specifically, blind spot ability. My lord, I had a match last 40min because of that crap. He would take all the purple and block any way for me to take out the tile.
Kishu. Caltrops.
'Nuff said.
Jean Grey - i always hit the match 5 jackpot when i play her
Anyone with cheap spammable skills like Juggs, Daken, Ares ect are the most obnoxious to me.
Thankfully Iron Fist hasn’t been brainwashed by The Hand because the thought of a node with him and a couple Kishu gives me nightmares.
Caltrops is by far the most annoying move, followed closely by “Turn to Smoke” - the Hand in general is designed to be very annoying!!
Loki and Jean for the same thing: you have to avoid criticals. Loki also match 4s but you can somewhat manage that matching a couple of his CD tiles or killing him, he’s squishy enough to not be that much of a problem.
But Jean… Accidentally got a cascade? Screw you.
You guys know nothing…
Carnage and his damn animations. Close second is falcon; but only during his PvP when you have dueling falcons going at it.