Dark Cucurucho seems to be rather sadistic, as they have been seen torturing Quackity in his nightmares, and laughed at him being terrified in their presence. Luffy has also demonstrated to be really scared of Dark Cucurucho[1], implying they've had a lasting negative experience with them. They seem to be motivated by a desire to create chaos, destruction and rebirth[2], opposite to the order their sibling believes in. This element of their personality is similar to The Watcher.
