Although Radahn can be defeated normally but I think this battle to Elden Ring Runes be the latest in a line of ridiculous FromSoftware boss fights that run much more smoothly using their unique mechanics , rather than take on the challenge as you would every other battle. For instance, think back, to Dark Souls III's face-off with Yhorm the Giant. You could whittle away at his huge health bar with your tiny weaponry all you want, but the developers wanted you to utilize a special sword in the arena to smash his looming cranium using wind magic instead. It makes what can be extremely difficult fight an easy one and feels appropriate in terms of thematics.
Radahn's battle in Elden Ring is also all about using the resources that are available to you. Remember how I said several warriors were gathering on Redmane Castle for the festival? That means that you'll have the ability to summon not just one, but not two but six NPCs to assist you in destroying Radahn. It's not like they can make the battle as simple as smashing Yhorm to pieces using Storm Ruler, but having Radahn's massive attacks focused on someone else while you perform hit-and run-style strafing attacks to your horse's own is much better than having him on your ass the whole time. Even better, in the event that your allies die - and trust me, they'll die frequently--you'll be able to summon them over and over. It's the law.
It's true that you can summon Patches into the Radahn fight too, but don't expect him to Elden Ring Runes buy stick there.
