I'm just happy this list actually contained HawkGirl...she seems to be forgotten in these discussions. I don't believe in Tier List's...but these are some of my observations through my experience:
Cyborg: Controls the air very well...very deceiving fireballs...
AquaMan: Can be seriously scary when up close and aggressive, however HG does not struggle against this character.
SuperMan: Frustrating character, good zoning...but I never thought he'd be considered top...
Green Arrow: Haven't played a good Green Arrow yet...doesn't seem too threatening
DeathStroke: A one trick pony, surprisingly good offense/up close game
Grundy: Scary up close...that's it
Bane: Same as Grundy
Wonder Woman: I haven't played an aggressive Wonder Woman yet (I've only played Mr.Mileena's run away WW) but I predict she will be much more heavily represented in the future...she seems solid with her B2 and her 33 low starter, her corner pressure is INSANE.
Raven: Can be difficult, negative on block, I think she is slightly over hyped...her trait is bad ass.
Killer Frost: Undeniably solid, HawkGirl has an easy win here
Harley: Shockingly not a good character imo, her zoning is blah
Black Adam: Annoying but managable
Sinestro: Crazy zoning...I don't care what Pig has to say about his negative frames, this character is nuts, IMO
Batman: Seems rather solid
Doomdsay: Crazy in the corner, seems solid, except that stomp is like Sheeva's
NightWing: I actually don't think he's good at all, contrary to popular belief, yeah his staff stance is great...HawkGirl could care less about this character
Lobo:seemed pretty solid when I played Reo's, apparently is not
Shazam: I play Emperor Gametime's Shazam (which is really good) so I find him to be an ok character, kind of annoying teleport, has a nice command grab.
CatWoman
retty Solid, have to be patient with strong zoners
HawkGirl: OP as fuck