I don’t know why but I’m super offended that you’d even compare the two.
Full disclosure, I lived in Anchorage when Keyes did (and when James Dale Richie did) so I felt particularly obsessed with both as it’s weird to be in a pretty small area with two active serial killers, and I have friends who worked with Keyes’s GF (not a PL, Alaska is just small in terms of population. Everyone is connected somehow).
Keyes is light years more intelligent and aside from being fairly impulsive (at the end) and very sexually deviant. Yes, Israel Keyes’ suicide note feels melodramatic. But not for the teenage immaturity that Lucas embodies. Instead, I attribute his gothic-y note tone to his psychopathy, narcissistic ego, and belief that he’s superior and the most important person alive, which is sorta Lucas, but not psychopathic. Lucas is incredibly emotional, but not empathic. Sexual sadists, like Keyes, are pretty empathic—they just don’t care. The whole point of sadists is wanting to inflict pain. So they are actually pretty attuned to the emotions of others (theory of mind is intact)—they just don’t care that it causes the victim pain. It doesn’t make them stop. It makes them keep going. Lucas lacks any ability to recognize the emotions or wants of others accurately much less care about them, because narcissism/immaturity.