The very first few times I went and tried to defeat Crawmerax by myself.
I died SOOOOOOOO many times, and it only took me a while to figure out there's a way to beat him. But that was days later after I got over how quickly he kicked my ass every time and calmed down. That guy sucks.
Another time was in Skyrim where I was fighting a Dragon Priest at the end of a side quest outside when a dragon and a fucking bear came at me. Apparently I wandered far enough away from the dungeon I was at that the bear and near by dragon wanted to know what I was doing. I didn't have a companion and I was royally fucked and dead not too long after they found me.

I died SOOOOOOOO many times, and it only took me a while to figure out there's a way to beat him. But that was days later after I got over how quickly he kicked my ass every time and calmed down. That guy sucks.
Another time was in Skyrim where I was fighting a Dragon Priest at the end of a side quest outside when a dragon and a fucking bear came at me. Apparently I wandered far enough away from the dungeon I was at that the bear and near by dragon wanted to know what I was doing. I didn't have a companion and I was royally fucked and dead not too long after they found me.