The first indication we get of Angier's gradual descent into Villain Protagonist territory is his kidnapping of Fallon to force Borden to hand over the keyword. Without hesitation, Borden hands over the keyword to get Fallon back, and completely loses it when he realizes Fallon has been buried alive. On a rewatch, this is even more heartwarming in hindsight—Angier just kidnapped and buried Borden's brother, so of course Borden would panic.
The other Borden reuniting with his little girl, Jess.
For all his flaws and obsession, the Borden twin who went to Angier's last show did try to save Angier, despite their feud.
While it was a huge dick move to take Borden's daughter after framing him for his own murder, Caldlow seems to have kept his word to keep Jess safe and content under his care, as she's no worse for wear during the last time we see her with him.
Every scene depicting the periods before Julia's death. It's both heartwarming and heartbreaking to see Angier and Borden as friends, Angier as a stable man, and Borden as not a Jerkass obsessed with secrets before everything went to shit.