Assassination was a tricky thing in this classroom. Normal assassination methods wouldn't work- seduction from junior high students to a probably (middle-aged?) monster was unthinkable, and sneak attacks couldn't even make the first step.
In E-Class, you had to adapt more than a usual assassin would. With the target's psychology skills, general intellect, and skills, an assassination attempt wouldn't be expected to work if it was just a single bullet trying to hit the head of the target.
Like painting with acid on a target's face or a poisoned soft drink, the levels of success varied with how unusual your idea was, an strage attempt on the life of an very strange creature.
So, playing to the teacher's weaknesses such as his fake value of the students, a suicide trap would be a successful one.
Karma had everything she needed for the attempt on the cliff- and only three things were needed.
Karma's life, the teachers faqade, and the fragile branch hanging over the forest.
Spin it all together and it'd make two deaths.