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!
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.
In fact, the implication that Gru seems to know every minion by their name.
Which is really saying something, since there seem to be hundreds of them! Can you say "Benevolent Boss"?
At the very end of the movie 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.
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.