Elden Ring lore portrays Starscourge Radahn as an extraordinarily powerful demigod, and his boss fight impresses that fact on the player, start to finish.
Not that the Starscourge was ‘weak’ to begin with Bad news, Elden Ring fans: Radahn is back to full strength.
Otherwise, the arena where you fight Radahn has summoning signs that allow players to bring in an unlimited army of NPC allies.
Players can (and should) use them to occupy Radahn while they prepare their attacks.