When a guy is trying to get a girl and succedes for a very short while.
After the breakup, they (the kornishin's) tend to act in a pathetic way to make the other person regret their choice. Which only worsens the relationship between the two people.
The person later thinks of the kornishin as no longer a friend and an immature individual
Alex: omg did you hear what happened to john and kate?
Mary: yea he decided to go all kornishin on her to make her feel bad
Alex: i know, what a pathetic loser