Pabongka Rinpoche (1878-1941AD) was one of the greatest Gelugpa Lamas of the past century. He possessed many spiritual realizations and was highly revered. He was the root Guru of both the 14th Dalai Lama's own principal teachers, Trijang Rinpoche and Ling Rinpoche; therefore, almost all the Dalai Lama's Dharma knowledge comes from Pabongka Rinpoche.
As the translator of his famous text Liberation in the Palm of Your Hand explains, Je Phabongkhapa had a profound and far-reaching influence on the Gelug tradition:
Pabongka Rinpoche was probably the most influential Gelug Lama of this century, holding all the important lineages of Sutra and Tantra, and passing them on to most of the important Gelug Lamas of the next two generations; the list of his oral discourses is vast in depth and breadth. He was also the root guru of the Kyabje Ling Rinpoche (1903-83AD), Senior Tutor of the Dalai Lama, Trijang Rinpoche, and many other highly respected teachers. His collected works occupy fifteen large volumes and over every aspect of Buddhism. If you have ever received a teaching from a Gelug Lama, you have been influenced by Pabongka Rinpoche.
Zong Rinpoche, also a highly regarded Gelug Lama, says on the blog mentioned above:
Kyabje Trijang Rinpoche and Kyabje Ling Rinpoche were tutors to His Holiness the Dalai Lama. They taught His Holiness everything from basic teachings to advanced levels.
Kyabje Phabongka passed all of his lineages to Kyabje Trijang Dorje Chang. He often said this in discourses. The purpose of this detailed exposition is to affirm the power of the lineage. If we lose faith in the lineage, we are lost.
We should remember the biographies of past and present teachers. We should never develop negative thoughts towards our root and lineage gurus."