What is your definition of Christian?
The defining aspects of a true Christian would need to include the following, as a minimum: (although this is not a comprehensive list)
1. Must be called by God and believe in one holy sovereign God, comprised of three persons: Father, Son (Jesus Christ), and Holy Spririt.
2. Must be re-born through God’s Spirit - transformed into a new creation in Christ Jesus and given a new nature from the one true living God.
3. Must confess they were born in sin, totally depraved and that their sin can be satisfied only by the blood of Jesus Christ alone who is wholly man yet wholly God.
4. Must repent of their sins and bear fruit which God has called all His disciples to exhibit.
5. Must look to the Bible as the inerrant Word of God and through the guidance of God’s Holy Spririt, the sole source for all teaching and discernment of the will of God.
I could probably go on, but these are certainly foundational. It should be noted that there are some religions that may adhere to these but often add to the gospel beyond what is prescribed in the Bible - this violation can be just as bad (or worse) than missing some of the primary tenets of faith.