To the best of my knowledge, it requires weapons of a supernatural aspect to do severe damage to the Ghost Rider (Zarathos or otherwise).The character has enjoyed a subtle increase in power level as Marvel has changed the way they handle their supernatural characters (Christianic mythology is utilized a bit more heavily than in times past).I'd assume Angelic weapons, major Reality Altering Entities, legendary weapons (Mjolnir for example), apex Demons ...