Dracula still has the human element of Gabriel Belmont during his interactions with the younger Trevor. While he's pissed off at God, and is willing to prove himself more evil than Satan, he still genuinely loves his son.
Marie's unwavering faith that the good man who was Gabriel Belmont still lives within Dracula.
Dracula: I've seen our son here. This is no place for a boy.
Marie: It's no place for you either, Gabriel... It never has been. It's time for you to go. It's time for you to return to us... To your family. Now you must drink my blood. It will help fight Carmilla's spell.
Marie:(intangible) Remember... I am always with you.
At one point, Dracula strokes the White Wolf that guides him between his past and present on the head.
That's actually a shout out to a similar scene from Bram Stoker's Dracula. In it, that Dracula calms a wolf that escaped from a zoo before he and Mina Harker pet it.
At another point, when collecting shards of the Mirror of Fate for the younger Trevor, he encounters the Toy-Maker. Despite being, well, Dracula, and despite the Toy Maker trying to kill him under the influence of the castle's corrupted blood, our protagonist ends up sparing his life after returning his clockwork heart to him, and encourages him to look after his humanity.
The Mirror sub-plot in general—even through it amounts to collecting pieces for a board game that younger Trevor's playing, Dracula does it anyway, speaking gently and patiently. To see the Prince of Darkness acting in such a fatherly fashion is one of the signs that somewhere in that monster's heart, Gabriel Belmont still exists.
Even if he calls him naive for believing in the Brotherhood's plan, Dracula can only speak of his old ally Pan with the utmost respect.
And he tries to talk Pan's brother, Agreus, out of fighting, not wanting to kill him. Considering that this is Dracula we're talking about here...
The fact that despite how dark he seems to be, you know, deep down, Dracula is the same good-hearted man he was centuries before.
When Dracula regains his memories of his Batman Gambit with Alucard, the first thing Alucard asks him is if he remembers their plan. What Dracula says next and the expression on his face just screams that Gabriel Belmont has finally come back from the dark side.
Towards the end of the Revelations DLC, Alucard shares a hug with Marie. Even though he's become the very thing he once fought against and still resents his father for what he did to him, he still genuinely loves his mother after hundreds of years.
The Ending: not only is Dracula redeemed in pretty much every way, he's earned the forgiveness of his son, the only (un)living creature that he still has any pure love for.
The Fridge Brilliance that the reason Gabriel Belmont remained God's champion even after he became Dracula was not an error of judgement on God's part. Gabriel ultimately destroyed both Zobek and Satan and saved humanity from evil. God's trust in His chosen champion was not misplaced. Reminiscent of Genesis 50, where Joseph tells his brothers "You intended to harm me, but God intended it for good to accomplish what is now being done, the saving of many lives."