Buck. After Max stormed off due to the anger that Buck started a relationship with a woman, Tara transitioned to Buck from the stress. And the first thing he did was break down into tears in a bathroom stall.
Hell, all of the alters become this in season 3, after spending 20 years of Tara's life and the last 2 seasons being the defining burden keeping her from a normal life, we see the sympathetic sides of them... just in time to watch them die.
Rescued from the Scrappy Heap: In season 3 Charmaine became a mother and finally matured by the end. This is especially evident when she turns to her mother and defends Tara, finally acknowledging that Tara's disease is very real, and that she has no real control over her alters.
Tara and Marshall are very easy to feel sympathy for with their respective mental health and romantic struggles.
In the second season, Pammy the bartender could also qualify, being a single mother and a love interest for Buck who's oblivious to his status as an alter. And then Pammy found out and couldn't accept that Buck was an alter and that Tara was the real deal. She burst into tears saying that Buck will punish Tara for hurting her since he promised he would never let anyone do so.