Well…since I nominated both Shadow Thief and Empath, and there seems to be some confusion, here's some info:
Empath:
Empath is from the Marvel universe. He's a mutant with the power to manipulate other people's emotions. For example: He has stopped fights from happening by using his powers...kind of like "You do not want to hurt anybody." and they will be like "Yes...you are right." He can also make people fight against each other and other stuff like that.
He was originally a villain, and was sort of arrogant. He even tried to control his leader, the White Queen, but she was not affected (I guess because she is a high level telepath). He did not show much regard for his teammates either. In one issue of New Mutants, there is the question of whether or not he is always using his power, even when he doesn't want to (at least on some level). However, over time, he became a better character when he fell in love with Magma. But, eventually, she left him (after a specific incident), and he said that she was his last chance for redemption. Then he walked away.
(He later appeared in X-Treme X-Men as a member of the X-Corporation, but I could never find out if the storyline finished or not - at least I could not find what has happened to him since - if anyone knows, help would be appreciated).
Shadow Thief:
My favorite DC villain. He has two origins, but I prefer his more recent, Post-Hawkworld one. I'm going to leave out a lot, but here is some of the more important info about him:
Carl Sands was an American who lived in Japan. He learned the arts of ninjutsu, and later became a world espionage agent. Afterwards, he became a more small-time ninja assassin/spy for hire. This was before he had any powers. He received a Thanagarian Shadow Field Generator from Byth (one of Hawkman's foes) which would greatly enhance his already excellent stealth skills. Using it, he could go intangible, phase through stuff, etc. He was warned to never leave it on for long periods of time, because there are dangerous side effects.
Recently, he became a bit insane from using the shadow field generator so much. He became paranoid and stuff...(check out Identity Crisis and then his appearances in Manhunter). After the long exposure to his shadow generator, Sands can now control shadows without it...but the full extent of his improved powers has not been revealed. He now seems to be able to regenerate his body, as he fixes a hole in his chest.
Although some writers tend to forget, Shadow Thief is a master ninja with great fighting skills. In the past, he has been defeated much too easily, but more recently, he has become a greater threat.
His personality is different according to who writes him. He used to be portrayed as a pretty normal person, despite being a ninja assassin/spy. He would sometimes team up with his enemy, Hawkman, when it was neccessary for his survival. He became a rambling crazy guy in Identity Crisis, and then in Manhunter, he developed a split personality (sort of like Venom - the host and symbiote relationship). He would argue with himself and stuff. He has not appeared since he got his power upgrade, so I am unsure about how it has affected his personality.
If I can, I'll try to scan some images of Empath and Shadow Thief. This depends on whether I will go home and get my comic collection or not (I'm far from home at college right now).
 
