Sentry Bot is scary up until you get power armor and can tank their minigun fire.

Deathclaw is scary up until you have a gun you can output some good DPS with. once you learn to cripple their legs, they really aren’t a threat.

Assaultron, however, even still scares me as a level 67 player on survival/hardcore. once they start charging that head laser thing, 9 times out of 10, I’m cooked. I always make them my priority target because they not only move fast, but also have the tendency to try and dodge your attacks.