I would say Aquarius would be the Violent Protest Leader, although Pisces might be the one willing to "die for the cause" in a martyr sense.
As far as Cult Leader? If it's all Charisma, Leo, if it's about religion and spirituality-Pisces. I could see Capricorn being an assassin if it was for a corporation.
Sags can't stay in one place very long so they could be a homeless vagrant that was still somehow ambitious.
Aries could be more dangerous if they wanted.