Beelzebub/Heartwarming

A minor one, but during Oga's fight with Tojo when Baby Beel attempts to assist him with demonic powers, Oga tells him to knock it off and comments that: "Even if I didn't have this contract, you know I'm not going anywhere." It's ESPECIALLY potent in context with the story arc, because previously Beel had severed the contract between him and Oga to prevent Oga from being killed. The minute he did, Oga left. Wonder if he'd do the same now?
Hilda thanking Oga after he protected her when she was seriously wounded.
In 75.5, there's this line by Oga. Made poignant because Beel was trying to be a man and defend a cat, who he saw as an enemy before.
This piece of dialogue:

Oga: What are you planning to do after you kill me?
Naga: I'm going to take master Beelzebub home.
Oga: What'll you do after he's home?
Naga: Our master, En, will be the one to destroy humanity, that's all.
Oga: Is that so?
Naga: Yes it is.
Oga: Let me tell you something good... Beel won't destroy the human world. Do you know why? It's because I'm his parent. I won't ever let him do something that stupid.

"You're the only father he has in this world..."
- Doubles as a Tear Jerker.
"As if I need a reason to help my sister!"
Oga, who previously showed nothing but resentment towards Hilda, is now willing to take on an entire army to rescue her. The look on Hilda's face says it all.

Shut up and let me save you!

In chapter 132, there's this:

Oga: The one that's fighting you right now...IS YOUR KING!

Oga comforting En when he thinks he's an unwanted child.
Cheesy though it may be, this page is just so damn adorable. No wonder everybody's moved to tears!
- Don't forget the Sleep Cute moment later on. Such a happy family.
Hilda calling Oga by his first name after getting her memories back. And it seems she'll be doing that from now on.
Kanzaki really does care for his little niece, as seen when he punches Oga in the face for making her cry.