Kick (one) when (one) is down informal verb phrase
To criticize, exploit, insult someone when they are in a weak position.
James has just got fired, so you shouldn't kick him when he's down.
I don't like my boss. He always kick his competitors when they're down.
Instead of helping Jimmy find his wallet, Jack kicked Jimmy when he's down.
Someone who ruins others' fun and enjoyment
The verb "kick" should be conjugated according to its tense.
This phrase is used to describe something very modern or updated or something that no longer looks like what it's used to.
It has been a long time since I left my high school, and now I have to admit that it's certainly not your father's high school anymore.