The word that the WTS translates "undeserved" is "grace" in other bibles. Notice this condescending response from the WTS.
*** w56 7/1 p. 415 Questions From Readers ***
? Is not the NewWorldTranslationoftheChristianGreekScriptures verbose, for instance, in using "catches sight of" for "sees" at 1 John 5:16 and "undeserved kindness" for "grace"?—J. S., United States.
You do not state whether you have studied the koiné Greek of the Bible or not, but, if not, then, because of your unfamiliarity therewith, the way the New World Translation Committee renders some Greek verbs and terms and expressions in English may seem strained to you or verbose. But not so according to one acquainted with the Greek. The Greek verb rendered "catches sight of" in the NewWorldTranslation is in a peculiar tense of the Greek language, the aorist, and refers not to a repetition of acts or to a continuing action but to just one instance of the act. The use of the present tense of the verb "see," namely, "sees," as in the KingJamesVersion, does not bring out accurately the singular meaning of the verb here in the aorist tense, the catching of a person, as you say, red-handed, in the act.
Likewise with the expression "undeserved kindness." It is simply because people do not understand the meaning of this Scriptural Greek word in its several uses that the New World Translation Committee made the meaning unmistakable by the use of the above expression. In English the word "grace" has fourteen or more different meanings. Which one does it mean, as at John 1:14 (AV), "full of grace and truth"? Does it mean there "gracefulness"? Or "favor"? Or "the grant of temporary immunity"? Or what? The NewWorldTranslation leaves no doubt as to the meaning but renders it "undeserved kindness," in keeping with the context, as, for instance, the succeeding verse 17.
So we appreciate the NewWorldTranslation for its attention to detail and its sincere effort to bring out the exact shade of meaning of the original koiné Greek rather than bring out a slipshod translation with an equivocal meaning.
Their probable souce of this thinking:
*** it-2 p. 155 Kindness **
*Joseph H. Thayer in his lexicon says: "The word [kha´ris] contains the idea of kindnesswhichbestowsupononewhathehasnotdeserved . . . the N. T. writers use [kha´ris] pre-eminently of that kindness by which God bestows favors even upon the ill-deserving, and grants to sinners the pardon of their offences, and bids them accept of eternal salvation through Christ." (AGreek-EnglishLexiconoftheNewTestament, 1889, p. 666)