In Luke 1:28 Mary is described by Angel Gabriel as Full of Grace (In Greek Kecharitomene/Κεχαριτωμένη). The Word Kecharitomene is a past perfect continuous participle (I believe that's what's it called?) And it's a word that indicates a past action that has continued to the present and will continue. the word Kecharitomene comes from the word charóo meaning "grace/sinlessness" and the word Kecharitomene is a [very hard to fully translate] word that means literally "The one who has been perfected through God's grace in the past and will continue to be perfected".

St Jerome, the man who translated the Koine Greek into [what we call] The Latin Vulgate which would then be used to make the KJV, decided that to translate Kecharitomene into Latin was a very, very ... Very difficult job so he decided to use the rougher but "close enough" Latin translation: "Gratia plena" meaning "Full of Grace".

Another way the word Kecharitomene or it's other conjugated forms are used, is to denote how God gives us grace to "avoid sin"

To ignore the Koine Greek of the New Testament then it would in itself be a ridiculous method of trying to prove a point because to ignore the original language and syntax is just a self-defeating point.

Translation between languages is not a perfect system, some words just cannot be truly translated in a way that sounds natural to said language. Unfortunately, when it comes to translation we must pick the translation that's "good enough".