Error!Sans is a major character in Underverse. With both him and Ink!Sans deprived of fighting each other, Error sternly tells Ink not to create any more AUs and that he won't destroy any more of them. With The X-Event on the loose, Error sees the truce he created, did nothing to stop Ink, and ends it shortly after his discovery.

Error may have a sensitive feeling towards others, but he's often shown to be remorseless, wanting to destroy all the AUs Ink cared about so much.