Is a mass-murderer who has a wife or girlfriend more lovable than a regular guy that has neither?

Insufficient data. If you're defining lovable as charming, comical and charismatic, you need only look to Ted Bundy as an excellent example. In my opinion once you discover he's a mass-murderer that instantaneously makes him less lovable than a 'regular guy'. I'll assume the mass-murderer in question here is a he since a female serial killer is a statistical rarity. If you assume a mass-murderer possessed sufficient social skills to land a wife and/or girlfriend. Then I would say since being more 'lovable' is a way to attract victims, he would already possess somewhat of an ability to refine that. I would say yes he very well could be more lovable. I'd have to take it on a case-by-case basis though lol. Perhaps the question you meant to ask is Is a mass-murderer who has a wife of girlfriend more inclined to be lovable (define) than a regular guy that has neither (presently or ever?)?

He may be very loving at the time to his gf / wife but is not a truly loveable person if he is a mass murderer.

The mass murderer may have a wife / gf because they are afraid of leaving him and also being killed.

The single guy may be more loveable and loved by more but just has not found what he wants in a relationship.

Was Hitler more loveable than Christ? Hitler had a mistress, Christ had neither.

easy answer, having a wife or girlfriend just proves that he is probably split personality and knows how to attract a female, he is still evil, evil, evil.

A guy that has neither could be very lovable.

Mass murderers are evil, and should be executed, regardless as to how nice their wives or girlfriends were.

No detail needed, nice guys finish last!

What a peculiar question.

i think that it's the same

no