Wiktionary
unbitter
a. Not bitter.
WordNet
unbitter
adj. having or showing no resentment or desire for revenge; "remarkably unbitter toward her captors"
Usage examples of "unbitter".
Anyway, he and Karkov had become friends and he had become friends too with the incredibly thin, drawn, dark, loving, nervous, deprived and unbitter woman with a lean, neglected body and dark, gray-streaked hair cut short who was Karkov’s wife and who served as an interpreter with the tank corps.
Tamman said wickedly, and watched both of them blush, amazed that he could feel such genuinely unbitter pleasure in teasing Harriet.