A person guilty of malicious setting on fire of property etc.

One word substitute is Arsonist.

Plagiarist: One who plagiarizes; or lifts the words, writings, or ideas of another, and passes them off as his or her own, thus engaging in plagiarism.
Anarchist: a person who believes in or tries to bring about anarchy.
Arsonist: a person who starts fires.
Nihilist: a person who believes that life is meaningless and rejects all religious and moral principles.