Answer:
In my opinion, I will definitely give him/her a punishment he/she will never forget. Like, I will show them that they themselves chose a temporary gain, rather than have me, a best friend, that they might have fights with, but is always there when they encounter situations that are hard to deal with, always trying to cheer them up, give them suggestions that they will definitely benefit from. They might have gained something, but that is only temporary, unlike me, who can stay with them for as long as they treat me well and with care.
I will show them how I can help myself, and not need someone who backstab me and use me as a stepping stone for their own greediness.
Explanation:
Watch out for wrong grammars, and I hope this example can help you all!
