I have woken up to choose pain and suffering
Remember this scene where Undertaker has said how much fun it is to have this job? Being an Undertaker, taking care of corpses every single day, seeing new faces with every customer that arrivers...
...Well how soon can said fun be ruined by just receiving a customer with a face resembling one of the Phantomhives after o!ciel left his parlor. Glad to head back to a job he enjoys just to be met with such a harsh reminder of it all. Imagine how cruel it would be to have to take care of a stranger's corpse that shares features with your loved ones, those loved ones that you are watching die one after another.
Perhaps it may be a reminder of Vincent. After all, a photograph alone brought him to tears (I'm aware that came far later...),
so how about an actual corpse that once had been so full of life, now just a cold lifeless piece? Not burned down to it's mere bones? An example of what a peaceful and later end could have looked like instead.
As for Claudiataker lovers, what if instead Vincent it might have been her? As much as I remember there haven't been photographs shown of her (correct me if I'm wrong). Perhaps Undertaker hasn't seen her face for quite the time. (I like to believe that all he has left on him is the memorial locket holding her hair and his very own memory not letting go of her face)
And therefore being hit with the resemblance of her face in someone else, like a repetitive stab to the heart, something he cannot die from, a pain forever for him to endure. Not to mention that the last two Phantomhives are both lost to him already. One's soul bound to a demon and another's possibly already long gone, having left a mere shell, or even puppet, to deceive himself with the denial of the end (and his loss) that already has been set for the Phantomhive family.
Fun fact I read Caitlin Doughty's book "Smoke gets in your eyes" (i love it SO much) and Caitlin writing about seeing a body similar to her friend's (that she realized she was in love with), I wondered how likely it must be for Undertaker to have experienced a similar thing especially considering how long he must have been working as an Undertaker.
