The
Golden Avenger.
Not only he has a few good counters to Erza stuff: Freon rays to handle fire, absorption grid to get most kind of energy, disrupt fields agaisnt electricity users, sonics to stun enemies, seeking missiles to counter HW's swords and power amplificators to match her in close combat.
But also better
suited in combat with all his weapon already in hand, while Erza need to switch between armors (I know that she can do this quickly, but is not as good as have a multi-uses knife), and Tony has a quick thinking to see her pattern style, and thanks to his experience with the Avengers he can figure out her game and
play dirty.
I doutb that she would go with this armors to the
Get
-Go, useless this is about life or death (Correct me if I'm wrong), the Wing Blade armor does not seems to bypass durability, it looks more like she can ignore distance (Since, she can cut without direct contact) and if I'm not wrong,
this girl doesn't seems to be sliced in half by the Nakagami Armor (Again, correct me if I don't know the context).
Erza could easily handle illusions (And maybe invincibility), but she will get a hard time dealing with his forcefields (Which he can amplificate as well) and armor resistances such a fire and electricity.
If I miss something then please tell me because I only see some clips of FT (Just clips, not actual episodes), but for now I'm going with the Merchant of Death.