Instigator

Near-synonyms: see Thesaurus:troublemaker

[T]he Pope doth not keepe his quarter, but will needs breake forth of the rayles and limits of that diſtinction, taking vpon him to be authorized alſo temporally, and that, for the ſuppreſſion and ſubverſion of the Civill Soveraignity, […] whence muſt neceſſarily ariſe either privie complottings, or open attempts, in favour of their opinions, and in furtherance of their deſires, which how farre it will extend, and into how deepe degrees it vſeth to grow, many ſorowfull and fearefull examples hath in this Realme demonſtratively declared vnto vs, to every whereof Papacy hath beene the ſtirrer and inſtigator.

[H]e [Jesus Christ] whom they deſpiſed as the Carpenters Sonne and bad come downe from the Croſſe, if he could, is exalted to the right hand of God, having all judgement committed to him, having before hand in his death, judged, ſentenced, & overcom Sathan the Prince of this World, the chief inſtigatour of his crucifiers, who had the power of death.

The author (obviously a naturalist of no mean order) received an official rap over the knuckles for trespassing, and for encouraging others to do so. Evidently the instigator of this reprimand had not visited the railway in blackberry time!

In studies designed to arouse aggression, the instigator often not only threatens the subject, but also expresses an extremely high self-evaluation. Subjects are insulted about their intelligence, sexual attractiveness, and character, and, at the same time, the instigator implies or explicitly describes his own superiority in these respects.

I love my lover. I do not want to be the instigator of anguish for her.

The instigator has the power to start the conflict. The person instigating the conflict always seeks power in some form. That is why they are starting the fight. […] An example of this is a child who tells two different kids that they are saying things about each other. This then starts a fight between the two kids, and the instigator gets to watch the fireworks. The instigator likes to feel the power of seeing the other two kids fight. In some cases, the instigator may want to redirect attention away from him- or herself and onto someone else.

Although each [river] restoration is unique, the genesis of most projects appears to center on a singular sort of individual that I have come to call "the instigator." Instigators are typically average Americans, quite often from a background that we would not consider a position of power. They are "housewives," students, small business people, retired persons, or a local politician or government administrator.