When we see three, we become uncomfortable. To be sure, there are those who call themselves Christians who deny the three. They are Unitarians and Oneness Pentecostals. Though if one does not confess the three-ness of God, the rest of the Christian traditions will warn you not only that you are out of sync with 2000 years of Christian understanding, but your very salvation may be in question as the Athanasian Creed ends with this warning:
"This is the catholic faith. One cannot be saved without believing this firmly and faithfully."