We human beings have no control over our destiny, and it is arrogant and foolish to think as such. Our fates are decided by a group of dark gods who control the strings of time. It is they who design a destiny for us, molding and shaping it to suit their purposes. No matter how hard we resist or what actions we take, it will inevitably reach the conclusion that they desire. Every few hundred years, a special individual is chosen to join this pantheon, either as a reborn god or a demonic servant. This is done through an artifact called a behelit, which requires a sacrifice of all those a person holds dear in order to activate. This artifact finds its way into the hands of an individual during a time of extreme tragedy, finally pushing the individual past the moral event horizon.
My protagonist has been singled out by this pantheon to become one of them, and has shaped his destiny in such a way that it would lead to him making that choice to become a monster. He is generally a decent guy, but is meant to suffer a large number of personal tragedies in life in order to slowly break him down, guaranteeing that there will be no resistance when the time comes. However, I don't want this person to appear as a sympathetic Sue who collects tragedies like baseball cards. It isn't supposed to seem as if I demand that the reader feels sorry for them by heaping angst on them one after another. How can I write this successfully?