The worst thing you can do to a person

The Kiss of Death for one's academic career especially if you are in Senior High School/First Year University. Anyone caught tend to be expelled and or blackballed from the college or campus in question... Rightfully so, too.

when a guy you love has sex with your best friend or any other woman/man.

When loser ex boyfriends with no dick's feel the need to call your best friend and ask her to give him head at the movies when your on vacation

Exploiting or using methods which are illegitmate.

What your ex did to you when she/he found a better puss eater

To take Adderall in order to study, do homework, pull an all-nighter, or take a hard exam