Not quite the same as it's a work situation - but it is someone I wasn't able to get rid of for years (and: I guess I was just too stubborn to quit a job I otherwise loved over them):
Eventually found myself crying in a corner - literally - about someone whom I outrank and outperform easily. For the sole reason that they had some powerful backers. I couldn't do it for myself - that's just not my level of self-confidence - but I couldn't and wouldn't take them hurting people I felt responsible for.
So I chose the war path! I went out, sought allies, went to battle ... and I won!
Now, my overarching point is not that! It's the following: I took it all, I took a lot more than I should have in the first place - and I hurt myself and allowed for others to get hurt in the process. The moment I was ready to fight back with all I had was the moment I stopped caring! I was, literally, ready to throw it all out of the window: a great career, financial security, a friendship network, a reputation that I had spent decades building. I was genuinely ready to toss it all over board, move somewhere else and start from scratch.
It was THIS that gave me the courage and the strength to finally fight back! It took the utter nonchalance of "so what, if I lose? I'm about to throw it all away, anyway! So I may as well go 'all in' on my final attempt!"
I can only recommend that you find your exit plan, OP. Yes, it may include huge personal sacrifices. But, for me at least, knowing I had other options was what eventually gave me the courage to push back with a vigour that meant I didn't even need my "plan B".
Long story short: figure out how you could get out - even if it meant burning bridges, leaving others behind, or risking it all. It's liberating, and it'll put you in a much, much stronger position to fight back.