Well, most of my characters are a bit crazy, but I have one that is very analytical, so this will be hard.
Name: Sabi
Species: Seviper
Gender: Male
Age: 32
Appearance: Sabi looks like a normal Seviper, but likes to make himself more deadly. He wears golden sheaths on his tail and fangs so they can stay as sharp as possible.
Personality: Sabi is an assassin. He will work for almost any client, but only if he considers the target a considerable challenge. Because of his occupation, he often works with criminals, like mobsters and terrorists. He is collected and cunning, and enjoys the kill, but is never overwhelmed by emotion. He likes to toy with his targets, and shows no mercy when eliminating them.
Background: Sabi was a born killer. At birth, he bit and killed his hatchling brothers and sisters, but his parents raised him anyways. At the age of 15, he finished off the rest of his family. He fled into the criminal underworld, where a Starapfor saw his killer instinct and took him under his wing as an assassin trainee. By 20, he had learned all he could from the Staraptor, and killed his old master in his sleep. After that, he came to the biggest crime syndacite in the world, Purgato, and killed their top hitmen, establishing himself as the best killer in the world. The leaders of Purgato however, refused his plea to join the group, but, one told him if he killed a Zangoose, a particularly powerful one who had trained for decades, he could join. Sadi killed the Purgato leader, but then went off to fight the Zangoose anyways. During the battle, he learned to ignore his rage towards the enemy species, and was able to easily finish him. He returned to Putgato, and was appointed the CEO's bodyguard and assassin. Through this, he has become feared around the world, and is also one of the wealthiest Pokemon alive.