Okay, I have had this thought for a while with two major armor wearers going toe-to-toe with each other.
Info: Erza Scarlet is a former slave and then became Fairy Tail's strongest female wizard. She possesses hundreds of armors with different effects.
Iron Man (a.k.a. Tony Stark) was a former weapons designer, but after being take. Hostage by terrorists and escaped, he decided to be go with the role of heroism. He designs many suits of armor with various abilities.
Location: Grand Magic Games Arena
Intent: to win
Restrictions: No Allies (except J.A.R.V.I.S. since he helps Iron Man's suits)
This fight will be divided into two scenarios.
1st Scenario: Erza vs Iron Man (Mainstream Comic Version) *Almost any armor
2nd Scenario: Erza vs Iron Man (Marvels Comic Movies)* Any Armor in the movies