Mora Pol, Dr.
The Bajoran scientist assigned to study Odo in his formative years at the Bajor Center for Science under Cardassian occupation had the changeling from 2358-65 self-described as the most rewarding time of his career. Although Mora had always felt fatherly toward the odd alien, he was shaken by Odo's rejection of him for many years until a bond developed after he helped Odo with an injured Changeling infant in 2373. Mora didn't realize the goo of 'organic broth' in his lab was sentient until it duplicated the Krokian petri beaker that contained it, and had no idea Odo was resenting all the tests he was put through.
The beginning of the end came when Mora, under intense pressure from the occupying Cardassians to get answers once Odo's sentience was realized, had the shapeshifter perform a humiliating 'Cardassian neck trick' for the visiting Cardassian High Command he had invited to the center in 2363; Odo walked out within the next two years in an acrimonious parting. Before the Founders were contacted, Mora lured Odo into probing his people's roots in 2370 on the Gamma Quadrant planet LS-VI; the resulting incidents helped finally start a tenuous bond. After the Dominion crisis deepened, he went to work on Earth at Starfleet to research new ways to help detect shapeshifters.