So, to answer this question:
If your Character was part of Ultimate Despair, What would they do to cause Despair?:
Use her research and aid work against people. What I mean by this is, if she was developing a vaccine, she would develop a more potent strain of the disease she was working with to release later as a bioweapon, and vaccinate her and the other Ultimate Despair against that strain. She would then release them all in busy places around the world. (Atlanta Airport, Beijing Airport, Tokyo, Shanghai, etc.) She may even bring back Smallpox, due to the fact that we no longer have immunity to it (I think.)
She would then work alongside the CDC, WHO, and Doctors Without Borders to assist with the massive outbreaks. Give people a spot of hope that they'll recover, and so that not everyone dies. However, she would also assist with conflicts over resources. She would deliver medicines anonymously to both sides of a conflict.
She'd also manipulate various CDC, WHO and DWO (Doctors Without Borders) and various officials to join in with her plan, so she can further spread disease and chaos.
What would their personality be like?
She mimics disease. Disease was one of the things that has ravaged humanity for centuries upon centuries. She doesn't discriminate, she's a cold and ruthless killer. She makes everyone suffer in their death, and does not care who you are: Rich, poor, black, white, gay, straight, Christian, Atheist. You'll still suffer in your death.
And she won't care at all.
What type of clothes would they wear?
Suyong is the type of person who, when releasing a Bioweapon, would wear a Plague Doctor outfit, and hide in the shadows and crevices, making people in that location think they were hallucinating a Plague Doctor. Otherwise, she would just wear normal clothes, and a HAZMAT suit to disguise the illusion that she was trying to help.
What theme would they have?
Unsure by what you mean by Theme. Her motif would be a Plague Doctor, or the First Horseman. Her Public face would be ordinary Suyong, assisting with the crisis, wearing HAZMAT suits, going into disease Hot-Zones, that sort of stuff. She might also occasionally use a White Horse in her plague motif, and call herself the First Horseman (Revelation 6:1-2).
If you mean Theme Song, it would be:
This, obvs.
Wow, I've thought way too much about this.