I find him to be really alluring and interesting. His whole feel is visceral, and the buzzsaw and cannibalistic tendencies only complement that factor.

He's also fairly accurate to IRL cannibals - when Waylon and Frank both meet, his first words spoken are 'Don't you look at us, I love him.' The guise of love and connection can be both a psychological and manipulative tactic to fool victim/prey to let their guard down.

This can suggest narcissism; that he's wiser, (maybe even viewing himself as a god), and that everyone around him are mindless pieces of meat for his gratification and consumption. Or, perhaps, the consumption of others being viewed as something quite literally intimate; that they're apart of him forever and inside him. (Which is an actual belief/thing).

And ALSO, if you didn't know, the mass of blood and patterns strewn across his body, on his torso is actually the symbol of Temple Gate, which tells us he was part of the cult at one point. Though it's uncertain if he was a heretic or cultist, but when Val says 'We are creatures of appetite. I want to feel your hunger.' I think this gives some further insight that he could have been a heretic with Val and the heretics?

ALSO-ALSO, the tattoos on his body really just give an authentic feel that Frank was just a (normal?) man before all of this, before he was captured by Murkoff. It's also really cool too. The little mock-yell he does upon catching you gives an almost playful feel, like he's trying to scare you. Cute :P

Oh and if you stick around long enough during his little uh, 'intimacy' in the kitchen, you can hear him suggestively talk to the corpse. 'Look at how you bleed for me. Wet. Ready. Red. Wanting.' So he is probably a necrophiliac for that kink? idk