You’ve created an awesome protagonist, someone the readers will identify with, root for, cry over and stay with for the duration of the story. The problem is that, without an antagonist, there is no tension. No challenges for the protagonist to overcome.
Come up with an antagonist who is equal in stature with your protagonist. Both have to have interesting backstories. Both must face challenges. Both have worlds around them. What makes the story move is when the stories and challenges intersect.
Just as your protagonist has skills and weaknesses, so does your antagonist. While the readers want your protagonist to be stronger of the two, there has to be enough resistance to make the protagonist work at winning.
Your task is to create an antagonist who is a good match for you character. This individual must be strong enough, talented enough, smart enough to be almost an equal to your character. Someone who will give your character a run for his money. Someone who will resist, who will fight, who will not go down easily.
Put them in a scene in which they will duke it out verbally, or physically if that is your wish. But however the battle occurs, it must be one in which readers will be fascinated by the story and read until the final word. In other words, the two characters must present a complicated relationship that, at the end, allows the protagonist to stand in the spotlight after facing a good fight.
Have fun with this one.