This concept is based off of an scp foundation wiki monster. http://www.scp-wiki.net/scp-231
An ancient deity called the scarlet king exists across several dimensions, but is prevented from entering our world due to a magical barrier. A cult formed in his name with the purpose of bringing him into the mortal realm to rule humanity by opening up a portal between dimensions, allowing his essence to seep through and take residence within an infertile cultist as a developing fetus. However, the gods essence is so massive that it cannot be contained within one individual, and must disperse his essence among other individuals in order to cross over. Thus, seven volunteer cultists were chosen to carry a "shard" of the deity, becoming what the cult referred to as the seven brides of the Scarlett king.
These seven were captured and taken in by secret governmental forces from the scp foundation, who seek to prevent these shards from being born through a process called Montauk-110. 6 brides died in complications during labor or suicide, with the seventh bride successfully giving birth after the sealing ritual failed. The coming of the Scarlett king caused calamity around the planet, with earthquakes, tsunamis, and other natural disasters spontaneously occurred with no explicable warning in various countries, leading to the deaths of 10 million people. The foundation have linked this strange occurrence with the birth of the child. Although powerful, it was a baby and weak enough to be controlled with the various incantations and sigils that the foundation laid in preparation for it, due to it being only 1/7th of the full god.
The child was raised by the foundation in an attempt to use its power in the service of humanity, but it escaped after a few years. This child grew up seeking to make a life for itself in the mortal world while being hounded by other forces: The cult who want to ordain him as their god, the foundation who wishes to use him for their purposes, and other groups who want to destroy him altogether. Through all of this, he has to come to terms with the fact that he caused the deaths of 10 million people, as well as other significant damage around the world. Killer's remorse is often looked down upon as a way to gain sympathy in order to not be held responsible for a crime, or for leniency. How do you get this across with a character without delving into self pity?