Assuming Calvus must follow the linear story structure, he could definitely defeat most enemies, especially with help. The puzzles aren’t too hard. I can’t think of any roadblocks, really.
each enemy take around 100-300 damage blows from the crew, Calvus has an attack that deals 1500 damage fully charged, there’s no way he can’t beat deltarune
thought this was gonna be like if he was playing deltarune rather than being a part of it nd my answer was gonna be “i think he’d have a stroke trying to figure out a computer”
given that NPCs take turns in Deltarune, he can just charge his 500! 500! 500! attack any time with no interruptions and effectively one move most enemies
not to mention he can block while being damaged, reducing damage by 50% regardless of using a skill or not