Asalaamu alaikum wa rahmatuallah wa barakatu
One thing I cannot stand (and there are many things, but in particular...) is hypocrisy.
I cannot tell you how many times I've come into contact with other Muslims who do things they are not supposed to do and don't do things they are supposed to do, and yet they have the nerve to act holier-than-thou and to lecture me and others on things!
What is this? "Do as I say, not as I do"?
Let he who hath not sinned cast the first stone.
Do not judge others, nor have the nerve to preach to others if you yourself are not doing as you ought to do!
Salam, O you who believe! why do you say that which you do not do? It is most hateful to Allah that you should say that which you do not do.