1 John 5:7 For there are three that bear record in heaven, the Father, the Word, and the Holy Ghost: and these three are one.
I'm sorry, but this is one of those places where, as they say, rubber meets the road, and we are forced to consider the fact that this particular verse appears in no Greek manuscript before the 14th century.
That's why most translations delete it, and so this verse correctly reads:
Of course, you can decide which to believe, but would ask the question this way: is it easier to believe that Trinitarians added those words to the text beginning in the 1300s, or that anti-Trinitarians somehow deleted them in all previous versions?