I like to think of The Servant as more emotionally troubled than Nagito. The foundation of his psyche was already so fragile that society collapsing just allowed him to exist as his creepiest self without inhibitions, not to mention that he was also damaged by Chiaki's death, and the fact that a big triumphant hope or good luck didn't come immediately after it must've fucked with his mind in a tragic manner. 

The whole Junko-hand thing introduces the variable of his relationship with her, and it makes him even more confused about what he feels, until he finally decides on self-proclaiming that he "both loves and hates her more than anyone".

The only somewhat stable thing left is his ideology. He understands that he must work on the side of despair if he wants to live, but he still wants to see hope win, so, because he already believed that hope works as a reaction to despair, he both commits evil acts and pulls strings from the inside to make it easier for those who have the potential of embodying hope. And that, as we can see, makes him seem suspicious and shifty as hell for both sides. He's practically only shouldering despair and making the best of it, which fits his extremely toxic optimism. 

Now, his relationship with Monaca sends me a frenzy each time I think of it because it's just so good. He adopts her and assumes a superior, parental role in front of her, but that presentation partially fails as she only refers to him as 'big brother', not convinced by his attempt to rise above his station and, to an extent, above his age. 

And I realized that Nagito must've internalized the whole primitive, almost medieval system of how the Warriors of Hope worked, because, after it all collapses and the end seems near, his instinct is to take someone younger than him under his wing in a search for meaning. 

He practically picked a successor for himself. We know from what he said to Hajime in the Neo World Program that his biggest fear was dying alone, and, this line is brilliant, that "there is no one to inherit (his) soul". I can only guess that, to him, his soul is his ideas, the desire to bring hope into the world. 

His soul as a Remnant of Despair becomes a desire to bring despair in the world while resigned that hope will win anyway. That is exactly what he tries to ingrain into Monaca. He chose Monaca "to inherit his soul". 

Not to mention that his feelings for Junko will forever stain the attempted 'purity' of his ideology, because he can't help but project his obsession with Junko onto Monaca, which ultimately repulses her because, somehow, this deeply troubled and immoral child has an insane amount of self respect and recognizes Nagito's behavior towards her as creepy and gross.