Mine wasn't just one session, just an entire campaign. I was using a Warblade from The Book of Nine Swords, in 3.5. I had other party members but they paled in comparison. One was a bard that used pretty much only
sleep, and the other was a ...honestly, I don't even remember. From the beginning the DM has a habit of targeting me with every single attack. There was a combat where I was attacked by 9 drow archers with poisoned crossbow bolts and had to make multiple constitution saves EVERY turn. My allies did... Nothing useful, and I took them all out single handed. Warblade maneuvers are OP. It also helps that I rolled very well in combats.

There's also been sessions where my character feels the other members are useless, and states this to their faces, multiple times, so he goes out and does entire sessions by himself. My favorite attack was called Mountain Hammer, and allows me to attack an object, and ignore it's Hardness rating. I've smashed full blades with my bare hands.
There was also a time where we were chained in the under dark for a while, then I realized that my Mountain Hammer works on anything I use to attack with. So I headbutted the shackles off of me, rescued my (useless) team mates, set my pants on fire, because I can't see in the dark, and then escaped relatively unscathed. Which led to me...
Being so mad at the Drow, I wanted to smash a hole from the ocean, into their massive network of caves, drowning them all. The DM was giving me multiple reasons why I can't do that, and I countered him every time. He told me that I would take loads of crushing damage, to which I told him I had potion bracers with 2 flasks of Cure Critical Wounds. Then he told me I would drown, but I also had a flask of Water Breathing. Then he told me what I got caught and lost, to which I replied that I had sun rods, that work underwater, and I also have a couple of immovable rods, so I don't get sucked deep underground. To which he replied, "Dude, just don't do that." So, we just walked away... I was so mad, that I had the ability to do this, but was shoved aside from the DM not wanting to change his campaign...
That was probably my favorite character I've ever played. When we had reached epic level, the entire back of my character sheet was filled with maneuvers and stances. Including a Feral Death Leap, that pretty much if I attack you, and you fail a massive Constitution save, you die. If you succeed you take, like, hundreds of damage... That Book was nuts.