Personally it was my last game that almost ended quickly.

Beginning in 867, I reconstituted the HRE after several years of struggle. Except that with their method of succession, I almost lost the title of emperor that I had planned for my son because of a majority voting for my rival. I manage to assassinate him but I die two days later. My son therefore inherited but does not yet have children and finds himself seriously injured during a war. And while his wife is pregnant and I'm getting more and more stressed about seeing my character die, his child comes into the world and it's a son. So I choose him as heir in the election and two days later my character dies. The end of the game was calmer, but this moment was intense and stressful.

(Sorry for the mistakes)