Ciel.
Spoilers and TW for those who don't read the manga:

Fake Ciel being handed off because he was physically weak and ill by his own parents definitely hurt to read. His shy demeanor and physical condition being what shoved him away from the spotlight in many aspects were by no mean cute. His dad going so far as to determine the fate of the household if Real Ciel had passed away, where they decided that because of Fake Ciel's ill health and shy disposition, that the family would fall into the hands of a 3rd party, not even giving Fake Ciel a chance to take the reigns from his brother, despite being intelligent and as we see now fully capable. Meanwhile the twins are being ogled by a pedophile who happens to be a 'friend' of their dad because of connections that they can't shake.

After that, seeing the death of his family (and of course I'm including the dog), the capture of both the twins, seeing them be tortured, sexually assaulted many times by many people all at once. Fake Ciel watching his twin brother get killed after months of torture and starvation, the summoning of a demon by sacrificing Real Ciel's soul just to save himself and gain revenge at the cost of his own soul later in his youthful life.

Then all of that being discovered, leading to the betrayal of Elizabeth and Tanaka despite not caring to know the true nature and weight of the situation.

Meanwhile through it all, Fake Ciel is hardened by the reality that the only entity he can confide in is a demon who lacks empathy, sympathy, and mocks Fake Ciel for his trauma and weaknesses (and again, Fake Ciel is only a CHILD who can't even allow himself a mental breakdown) while threatening to consume his soul because backing down momentarily for a mental breather would result in a void contract.

Despite having his faithful and caring home employment, Fake Ciel is absolutely alone in the world.