When I have people that get on my nerves, complaining all the time.
About any and everything - including the weather, that they have No control over.
The way I figured out how to stop all that:
Interupt them while they are talking, find one thing to compliment them on.
Example: Sorry for interrupting, but that is a Gorgeous _________! where did you get that from?
They like that you paid attention to them and noticed something good about them, and by time they look at it,
Say something else and start the conversation in a totally different direction.
I noticed in my experience that this interrupts them from 'dumping' their load of negativity on me, stops them
from complaining, and they go on about their day - in a better mood.
Call it a Public Service. I did a good deed for them. AND for Me!