A Fullborn is just so much better than a full Radiant. If the Radiant gets their powers by using a combination of Honorblades rather than bonding the spren to gain the powers (which seems like it’s possible, just unlikely), they’re a bit better, but still nothing compared to a Fullborn. If a wielder of multiple Honorblades fought a Fullborn with sufficient metals, the Fullborn wins hands-down. We know Honorblades use stormlight faster than conventional Nahel Bonds, and using more than one would drain stormlight and an extreme rate. A Fullborn with full metal minds and enough metals to burn is basically unstoppable. They can heal from anything, with virtually no limit as long as they have enough gold (Compounders are way more powerful than conventional Bloodmakers), and they have enhanced strength and durability from pewter. Add temporal manipulation and Atium, along with duralumin fueled steel or iron, and Compounded speed, and the Fullborn outlasts the Radiant 100%, especially if they can Leech the Radiant’s stormlight. The fight would be close, and I don’t think gold can heal a wound from a Shardblade, but I’d say the Fullborn would win in heated combat, especially with Atium.