Playing Star Wars 5e, short campaign, first time DM, we did fine for the whole 3 games we played, all four players were playing fine, taking smart choices trying to make it the best experience for our friend who was dming for the first time ever. All until we got to the end of the campaign, time to confront the big baddie. I missed an investigation check to spot a trap, we take massive damage, dm tells us to roll initiative, we all roll really low (under 5), DM says we see a laser coming from a vantage position, starts rolling multi-attack, 3 straight nat 20s, massive damage rolls, 3 out of 4 members of the party died instantly, me included. The remaining member was a doctor, we felt we had a chance… DM says the big baddie has legendary actions. After around 12 hours of gaming, across three days, we all died in less than 10 minutes. Fun times, we still make fun of him whenever we remember. The worst thing? I took a look at the encounter later, it was not even that badly tuned, it was really just piss-poor luck.