My First 4e death was the first Gameday wizard pre-gen. Fey stepped onto a raised area, wanting to push an evil wizard off so the others could get him. Couldn't remember the Bull rush rules at the time and instead did a magic missle. I should have spoken up and asked how to do it. Instead, the evil wizard bull rushes ME, and shoves me off, fall damage, and then surrounded and pounced by skeletons, leading to a near TPK, my wife's rogue managed to run away.
As a DM, I essentially TPK'd a party in LFR. Was running the mod with the Ugly Calisham girl and all the were creatures. In the busted up courtyard, first combat, the party didn't focus fire very well, and I took advantage of staying up high and using range attacks while the guys on the ground were hitting hard and focusing. As the party started dropping, the cleric was crawling around (knocked prone and very hurt) and doing heal checks to get ppl back up, just so i could knock them back down. After some attrition, it was just 2 party members left, one a single hit from falling again, and the crawling cleric whoe was at 1/4 hp, versus my ranged guy making a fighting retreat. The ranged guy still had the upper hand, seperating the cleric and the other guy with distance. Not wanting to kill the party in the very first combat, I had the city watch show up due to the commotion and finish the fight. Most of the party were on thier last death save attempt and probably would have failed the next round. DM mercy is the only thing to save them. Of course, one player RPing a jerky character derailed the rest of the mod and they failed anyway.
Another game, while not a kill, I did an impressive amount of damage to a monk and the rest of the party. I was currently experiencing a severe allergic reaction to something and through out the game i was starting to puff up all over, but that never stops a dedicated DM. Instead, during the first combat, I managed to channel the necrotic energy of my body fighting itself and feed it into 9 criticals during the first encounter, in 30 minutes, 7 of them against the same player (monk). Just about every single roll I made hit the players, the entire evening, and either crit, or rolled max damage the hard way (or a few points shy of max). There was a ton of healing on the table and healing surges were gobbled up like candy. My wife started stealing my death dealing d20s so the party could survive, but even my crappy-rolling d20 was rolling high. After the game ending at midnight, I went to the hospital by 1am before the allergic reaction finished spreading across my chest, killing the DM. I forget if the next game was the day after or the day after that, but i couldn't roll a hit on anything to save my life, as the necrotic energy had been depleted by modern medicine
The monk's player still vows revenge when she DMs
