One big unicorn, strong and free, thought he was happy as he could be. Then three little kittens came around and turned his whole life upside down. They made him laugh, they made him cry. He never should have said goodbye. And now he knows he can never part from those three little kittens that changed his heart.
And trying to convince Margo to jump from Vector's ship to Gru. He promises her "I will catch you...and I will never let you go again."
After Gru finishes his book, he gets up to leave, stops for a beat... and kisses the girls on the forehead! Awww...
But wait—it gets even more heartwarming! When Gru reaches Margo to give her a bedtime-kiss, the girl (who said earlier that "Just so you know, you're never gonna be my dad" and also hesitated to jump over to Gru) suddenly jumps up, flings her arms around his neck and whispers "I love you..." and Gru replies "...I love you, too."
And after that, his minions are waiting outside the door, each one wanting a kiss too! It becomes SO heartwarming, it goes back to Funny again!
For context, Gru refused all of the girls' previous requests for goodnight hugs and kisses. Seeing him finally do it, without being asked, shows how far he's come from the start of the film.
An earlier, less obvious CMoH, but Agnes giving Gru her piggy bank after the Bank of Evil stops funding him serves as this, and also leads to the most uplifting moment in the entire movie. The minions also show their loyalty and love for Gru by offering up their savings, because they're not about to just give up on him!
The minions' "toy unicorn" counts when Agnes kisses the minion's goggles.
As does the sheer delight on his face.
The montage where he starts to enjoy and get used to the little girls' presence.
When they showed the wall with Gru's family tree, and the heart around Gru and all the girls' doodles.
The first time Gru refers to a minion by their name, you can't help but pause and D'Awww.
It's implied that Gru knows all of the minions by name! And there are literally hundreds (possibly thousands) of them! Can you say "Benevolent Boss"?
Credits bonus: a Minion appears in silhouette and makes a hand puppet to somehow resemble Gru, and imitates his voice, going 'I am Gru. Back to work! Back to work!' Gru appears and the Minion quickly retreats off screen...and then Gru chuckles. Not only does it show that he's a softie underneath, but he genuinely appreciates his minions.
Marlena showing the girls Gru's baby pictures. This is the first time in the movie that she has shown a soft side...and its to her granddaughters.
When Gru is forced to take the girls to their ballet class, Agnes hands him a ticket to their recital and asks if he's coming. Gru sarcastically replies he's excited, and Agnes makes him pinky promise he'll come and Gru (again sarcastically) does as well. The sweet part not only comes from Agnes's interactions with the grumpy Gru, but also how the mothers of the other ballet dancer react: With a look of heartwarming respect of a father and daughter.
The girls' ballet teacher allowing a few more minutes to wait for Gru after seeing Agnes' Puppy-Dog Eyes.
The ending, with the girls doing their ballet over again in Gru's lair, is chock full of this:
Gru commenting on the girls are very good during the recital.
When Gru's mother admits that Gru is a good parent...maybe even better than her.
Gru's expressions through that whole scene just sell it. At first he's annoyed at her glib behaviour, but when she amends her statement, he gives a small, warm smile.
A small one, but Dr. Nefario, the same man who didn't hide how the girls' presence were distracting Gru and called Miss Hattie to take them back without telling Gru, is see with a recorder during the recital.
The very last scene — Gru and the girls are escalated to the top of the house and watch the moon in awe. And during this Gru picks up Agnes and puts her on his head while Margo holds his hand, and Edith is seen grasping at her his legs.