Roman Catholicism is probably the largest and most well known christian sect. However their traditions and practices are not biblically based. Off the top of my head. The veneration and offering of prayer to or through Mary. Having to go through a priest to be forgiven of sin. The fetishization of the bones of saints and other "holy relics", the crusades..... Etc. All this and more is the exact opposite of what Jesus preached. So how can you say jesus is your lord then turn around and do the exact opposite of what he says and then give your "church" more authority than God? Tldr- Catholicism is a sect, is completely unbiblical and has done more to turn people away from the bible than all of the roman emperors combined.