Does good Karma guarantee liberation?

The short answer is No. One gets liberation either by exhausting all of their Karmas or working towards liberation through meditation and prayers and other yogas (Karma Yoga, Bhakti Yoga, Dharma Yoga, Ghana Yoga). But good Karmas do have its advantages. Depending upon the type of Karma that ripens at the time of our death, we take rebirth in a particular realm. So if we have more good Karmas then negative Karma, chances of our good Karma ripening at the time of death increases resulting in a better rebirth (relatively speaking as all rebirth create suffering).