The term for a person who kills a king is a "regicide."
Wife..
A person who kills plants is generally referred to as a "plant killer" or someone with a "black thumb."
The organisms which eat insects are called insectivores.
A person who kills a lot of people is typically referred to as a mass murderer or a serial killer. These terms are used to describe individuals who have committed multiple murders.
Finance
An assassin (assassination is the action of doing so). Simple, but answers the q
rich
When you shoot someone on the opposing team and one person on your team kills the person you shot. It's short for assisted kill though
You should call her by her first name. You may refer to her in third person as your sister-in-law.
Uxoricide
A person who commits suicide is also called a suicide. Or..."dead" is probably a good word for it. :)