A.T. Robertson Commentary Galatians 4:16

"So then am I become your enemy, by telling you the truth?" — Galatians 4:16 (ASV)

Your enemy (εχθρος υμων). Active sense of εχθρος, hater with objective genitive. They looked on Paul now as an enemy to them. So the Pharisees and Judaizers generally now regarded him.

Because I tell you the truth (αληθευων υμιν). Present active participle of αληθευω, old verb from αληθης, true. In N.T. only here and Eph 4:15. "Speaking the truth." It is always a risky business to speak the truth, the whole truth. It may hit and hurt.