Hamnet
Having Agnes reach out to her son grown up just to watch him die again except this time sharing the grief with the rest of the audience so that they may feel even a sliver of what she must’ve felt during her last moments with him.
She was able to see that William was grieving in his own way and he was “there” this time for his death.
And also having William look back at Agnes like Orpheus and Eurydice.
And also the Arrival soundtrack at the end.
Man.
Yeah it was ight