Could this be the most convicting verse about peacemaking?

I can’t stop thinking about what I read this morning in Jude:

“Behold, the Lord comes with ten thousands of his holy ones, to execute judgment on all and to convict all the ungodly of all their deeds of ungodliness that they have committed in such an ungodly way …” Jude 1:14-15

What could have been so awful? So sinful?
 

“These are grumblers, malcontents, following their own sinful desires; they are loud-mouthed boasters, showing favoritism to gain advantage.” Jude 1:16

I can’t stop thinking about this. What is so awful? Complaining and being ungrateful.