Thinking about that scene makes me want to cry. All the other moments people mentioned hear also tear at the heart strings, but for me, hearing that little girl yell and cry is just too much.

Not the absolute saddest but when Birdy goes to find a dress to wear to her momma's funeraland takes a big inhale smelling a dress and starts to cry.

They do. The last scene has Justin rough housing with him while the four of them are walking down the street

Not the saddest parts but when she sees her aging father in the elderly home and he has a picture of his granddaughter. He speaks for the first time.
And the little boy. Poor little guy. Mother abandoned him. His granny died. Who is left for him?? I hope that Birdie and Harry Connick Jr take care of him.

I have to mute it. It's gut wrenching. Having a daughter and having been divorced, I just have a hard time with that scene.
A little part that always makes me sad is when she talks about seeing herself through Bill's eyes and getting smaller and smaller. I told my ex that resonated with me, and he didn't get it.

I loved the way Birdie stood back and let Dad do the damage, let her daughter feel the pain, then went and scooped her up, and brought her in the house. I know it was probably the hardest thing she had to do as a mother; I'd bet her insides felt like ground beef the whole time. But she showed her daughter that even through the worst parts of life, a person can stand on her own, with dignity and strength of will. So sad that some people have to learn that at such a young age.
And, yes, both actresses were amazing.

I crawled in bed with my daughter after that scene and just cuddled her for a minute. That ripped my heart out, and mama bear in me went in to "the baby is crying, destroy whatever is making the baby cry" mode.
The actress was incredible in that scene.