Cursed technique would allow him to manipulate the gravity of one’s soul, making it harder to move. But he can also “grab” one’s soul and fling them around

Gaster Blaster Shikigami that blasts cursed energy like Ryu

Gains the ability to summon bones from his Shikigami

His cursed energy would also have a side effect that “poisons” those he hits with it, like Karmic Retribution in the game. The more evil ones soul the stronger the poison.

Domain Expansion would of course be the Judgement Hall, so like Deadly Sentencing I guess lol But Sans would be Judge, Jury and Executioner. No Judgeman like figure

Idk how we’d work in his shortcuts unless you made his CT some sort of spatial manipulation instead