I assume you are an adult and are reasonably strong?
The reason he refuses to be tame is the boy taught this iguana how to resist humans. He probably dropped it whenever it acted out, or backed off when it did wide-open mouth hissing threat displays. Now his weaponry (teeth, claws, and tail whips) is so strong he can resist even an experienced handler like you. The boy may have retaliated with negative feedback in some way which would have made things much worse.
When it was ha hatchling, this ig should never have fallen into the hands of a person who wasn't up to the task of taming and socializing it. It happens to tens of thousands of poor helpless iguanas in the US every year, and they all end up in trash cans. Few people are willing to keep a violent, display-only iguana.
Now this iguana legitimately hates humans and is a real tough case even for experienced iguana rehabbers. He may be a lot smarter than you think, and be more stubborn than you can imagine, and you may not have yet experienced a display of his full strength.
The first thing is to back off for a month or two, only going in his cage to clean up, feed, and water him. Hopefully he has a way to roam around on his own?
You need protection. I wish I could give you the URL's of online stores that sell protective gear, but you can fid them. Look for knitted Kevlar gloves, or Spectra knitted gloves, which have yarn that includes a thin strand of stainless steel wire. Sometimes they are sold as knife-safe gloves for filtteting(slicing) fish or shucking oysters. Also find knit Kevlar 'sleeves' that have a thumb-hole and stretch from your hand to over your elbow. They don't need to cost much, and don't have to prevent peg-like teeth from penetrating (as with gloves for handling skunks and raccoons), because iguana teeth form a unique very sharp knife edge. This type of glove is very good at preventing igs from biting through. This setup also prevents the claws from sliding over your skin cutting bloody grooves.
The next trick he learns could be to bite at your face, or tail-whip your face. He is very accurate with both weapons and he learns fast, so always be very alert and careful.
Negative feedback is only destructive and I can explain why. But I'm The Boss often does work if it's done right.
Baby igs use all their weapons to resist being picked up and tamed, but they can't hurt you. Before they are strong enough to damage you, they are already tamed. The hard thing is that you have to do the same things with this grown violent ig. it may seem impossible but it's not, if you have the fortitude to do it. You will have to learn how to quickly pick him up, and how to hold onto him while you carry him to a sofa. Once you can do those things you are on your way. I would have to give you a lot more advice before you started with it.
The theory is that all iguanas of all ages and temperaments can be at least tamed, and many can be socialized. In practice though, some igs can't be tamed. One lady tried her best with her grouchy adult male, with skill and high-level advice, and lost a finger when he bit down on it and alligator-rolled. Other people can't handle the violence, as there is no proven soft, slow way to do it.
I have to go now. If you want more, I will work with you.