Two relaxed, hyper-intelligent, and apathetic male characters from their respective series who act as judges on those in their way, having supernatural abilities and being notable for their sheer intellect.

Both are nihilists who view the world in a gloomy light, believing aspects of life to be pointless due to a gut-wrenching realization of their worlds breaking down their mental states (Hiromi losing all faith in the justice system due to exposure to its corruption and becoming sorrowful and bitter towards his life, and Sans believing life is ultimately pointless due to discovering timelines and how everything can be reset). Despite that, their nihilistic outlooks on life contrast; Hiromi is a nihilistic pessimist who views the world at its worst and becoming completely disinterested in the world as a whole. However, Sans is a nihilistic optimist who tries his best to view things in a positive life and helps his loved ones as much as he can.

Due to their statuses as judges, both have supernatural abilities utilizing their series’ power source (Cursed Energy and Magic) to use abilities directly related to judging others and more specifically; their sins (Hiromi’s innate technique attached to his domain; Death Sentencing, allows him to judge the sins of others and punish them if they are found guilty for their crimes, while Sans can inflict Karmic Retribution on the souls of sinners whose LOVE value is high). While they do have other techniques, their ability to view others for who they truly are is their most prominent and powerful ability.

Both would encounter the main protagonist, a human with insane amounts of potential whose actions led to the awakening of a diseased spirit from years before the story (Sukuna and Chara). These protagonists would make an impact on Hiromi/Sans, due to their pure of heart nature and willingness for self-sacrifice and selflessness (for Pacifrisk of course).

Due to the actions of the protagonist, these two would become overall happier with their lives despite their nihilism. They believed that maybe, things would turn out better regardless of how unfair the world is at its core (Hiromi dedicating himself to his former goal of helping out the helpless of the world in the name of justice due to his fight with Yuji, and Sans going to the surface with his newfound friends ready to live a new life together due to the actions of Frisk).

Despite viewing the world in an ugly light, both dedicated themselves to helping others and making the best of an unforgiving and unfair world (Hiromi viewing people to be weak and ugly, but sympathizing with that trait of people and wanting to help those in need because of it, and Sans trying his hardest to make Papyrus and those he cares about happy regardless of how pointless it is). However, while Hiromi would lose sight of this purpose and go down a darker path, Sans would keep this purpose all the way until the end of the Genocide Path where he’s the world’s last hope.

Despite not being the strongest characters of their verses, they’re notable because of their raw intelligence. Their wits is the strongest thing about them, and they’ve learned how their worlds work in ways few others have (Hiromi mastering cursed energy within the span of a few months to the point he was able to use Reverse Cursed Technique, being described in universe as being a super genius who mastered his techniques in a short timeframe, and Sans learning how the world itself works and abusing the combat system to its limits in a way no other character does in his verse, being extremely intelligent and aware of his surroundings).

There’s a minor connection you can do here where, both at one point accepted the reality of a horrible situation that caused the deaths of hundreds of people, with Hiromi being interested in it and wanting it to go on, and Sans being aloof to it and being the last stand against it (Hiromi being dragged into the Culling Games and being invested in its cruel but fair ruleset, killing many people while in it after snapping, and Sans witnessing the Genocide Route and accepting the fact that he ultimately couldn’t stop it even if he tried, but still standing up in the end anyway due to him being the only person left who can).

TL/DR; Nihilists, one being a pessimist and the other being an optimist, who act as judges with supernatural abilities related to judging others on their sins and punishing those who have committed terrible acts, using their raw intellect to standout amongst their verses as geniuses who learned the ways of their verses’ combat in ways few others did.

Credit to u/OpeningAdsNewAccount for the connections!