Magic form
Actually we know thats Curse users can’t be damaged with weapons and fightning styles right? But have you thought why? As far as we know from the lore and the battle with Curse users (Rupin, Arsen, Trigno) we know that they have a human form and magic, in magic form (combat form) they are invulnerable to weapons and fighting styles not related to magic, but not did you wonder that Curse users also somehow have to replenish their magical energy. Given that they take the form of their curse, it is possible that they take energy from the environment directly, but in a different way and not like the player (the player charges his energy storage while stopping and not moving at the same time), with this option everything is useless.
Exhaustion Theory
Well, to the point, if there is some kind of limit, or the energy in the atmosphere can be exhausted, then in this case, with a very long and exhausting battle, the enemy using weapons or fighting styles can, so to speak, exhaust the enemy to such a state that he cannot will transform into its magical form, thus giving you a moment to attack for a short while, since as far as we know from experience with Ramses II, a Curse user outside of his magical form can be injured or even killed by a weapon or fighting style. In practice, this option is not possible due to the disproportionate strength of the Curse user and the weakness of the weapon and combat style users, but even so, it is possible someday purely logically this will happen. So if you are a very strong user of weapons or fighting styles, then fight for hours and days until your opponent loses his magical form, and until then just block and dodge all attacks.