Try #keithcunningham and "a road less stupid" it will be invaluable to you!

The Challenger Sale?

Start with this: and its companion "Crucial Confrontations":

„Give and Take“ by Adam Grant

Winning Through Intimidation by Robert Ringer. It sold poorly when it was first published because of the title, but now people value assertiveness. You don’t actually have to be a jerk — but it helps to recognize when others are.

The Courage to be Disliked might be the one you’re looking for

There is often an underlying psychology issue if you avoid confrontation. Might be worth checking out this book. It's also a quick Audible listen. Gave me perspective.

A few pages in „Run Studio Run“ and „Company of One“ could be relevant.

2. Crucial Confrontations: Tools for Resolving Broken Promises, Violated Expectations, and Bad Behavior

Two books I found useful: Crucial Conversations: Tools for Talking When Stakes are High, Third Edition and..