if it's not the boss and it's something that i can't handle on my own, i tell the boss in a matter-of-fact way. bosses don't like anything that interrupts work getting done, so frame it in that way and they will try to help.

if the problem is the boss or someone above the boss, you remain diplomatic and document everything you can. sometimes just doing that is enough and you can ride it out for a long time. other times you'll want to plan some kind of exit strategy like a transfer or new job.

in my experience a shitty/rude boss can be dealt with even long term, so leaving isn't necessarily the first option. but with a boss who is out to get you - and by that i mean goes out of their way multiple times to start conflict with you or make you look bad in ways that are inappropriate and unnecessary - usually leaving is the only real resolution.