Frank comforting Scarlet after the revelation of Gabriel's evil.
Doubles as a Tearjerker. Karra gives a We Can Rule Together speech to Frank in a hope he will take him up on it so they don't have to fight, even though both of them know he won't accept it. Karra also spares Frank's life repeatedly despite him being the one giant threat to her plans to resurrect her father, because she loves him.
Frank's choice to save Karra even though it will mean Longinus' resurrection.
Longinus thanking Frank for saving his daughter and even saying he owed him one, effectively ignoring the fact Frank had to kill Lilith to do it.
At the Gates
Frank's intense, overwhelming love of his mother shines through on virtually every page.
Echoes of the Past
Frank's love of Karra is the first thing he thinks about when he's told he's the new King of Hell.
Beyond the Veil
The discovery by Frank that Kara is pregnant and what this means to him.
The quiet domesticity of Frank and Kara changing their babies' diapers. Quickly becomes a Tearjerker though.