How to not be intimidating
Standing proud and tall communicates to the intimidating person that you can't be pushed around, that you're sure of yourself. As social psychologist Amy Cuddy discusses in her well-received Ted Talk, good posture actually can the feelings of confidence you hope to portray. Science has proven that there are "mirror neurons" in the brain that respond to elements like facial expression and contribute to empathy, so if you adopt an approachable demeanor, you can get back what you give.
But you can identify the main points you want to bring up and practice saying those in a few different ways.
“If you want to be less intimidating, take practical steps that rework your image in another way using things like body language, emails, less curtness in interactions etc.” One strategy you can try is to take a little more time with each workplace interaction than you normally would.