I think kids can be much more evil than adults sometimes, within their own gaming constraints.
When I was seven or eight (in grade-school or thereabouts), I remember how I used all the other little school kids as experimental subjects.
I recall one particular day when I concocted an entirely valid excuse to go see the principal during class hour, so I could be at a certain location at a certain time.
I don't even remember what the excuse was, except that the timing had to be right for me to be exactly at the corner of the building's balcony, near the stairs.
The balcony of the school on the second floor had a certain gamma shape:
After I talked the principal to death, she'd let me go, and I'd go hide at the X location, around the wall's corner, waiting for the bell to ring.
After the bell rang, all the happy little kids rushed out of their classrooms en masse, yelling and shouting happily, in the direction of the arrow.
A little before they reached the corner near X, a little foot, my foot, projected forward from behind the corner, just above the floor. The first happy little kids tripped on the unexpected foot and fell on their faces, sliding forward until they hit the wall.
The kids that followed, tripped and fell upon the already fallen kids until the greatest percentage of the exiting kids accumulated in a cannon-ball configuration near the wall.
I then observed and examined the fallen little kids with great pleasure, trying to see how fast they would get up and what they'd do.
The poor kids were of course so full of desire to go play in the yard, that they didn't really care, so they got up and continued their journey down the stairs to the yard.
Hence, I repeated this little experiment several times on the oblivious happy little kids. Same result every time.
There's nothing more natural than many, happy little kids, wanting to go play outside after the brutal torture from an hour of grade-school class nonsense.
There's nothing more evil than having a little kid who instead of wanting to do the same, incapacitates many happy little kids who want to go play, en-masse, using their own kinetic energy (to minimize energy expenditures), so he can observe and record their reactions.
I think the principal called my father back then and told him what I was doing. I never found out my father's reaction, but I suspect it wasn't very good.