Instigator

Instigator

<in-stee-gate-tor>

troublemaker; agitator; initiator;

a mastermind who motivates other people to do things.

Don't be an instigator and encourage them to break the windows.

Memory trick:
Instigator reminds of aligator
an aligator is aggressive animal

At work:
Don't invite him to the meeting. He is an instigator and he will make everyone argue.

(c) 2015 E. Carruthers