I just added this (only four months later!). Seems likely that it's a record for most deaths of a single character in one raid.
While I have no doubt that this is probably the record for most deaths of a single character, I think I might have the record for most deaths by a single press of a button.
It was on the Infinity server and it hadn't been too long after Infinity learned how to take down Hami but I don't recall the date.
My character was called "Shade of Night". I had just made it to level 47 on my Dark/Dark defender and my SG mates took me to my first Hami raid ever.
The taunt team was doing its job and the Illusionists were drawing the fire of most of the Mitos. We were clearing out the Mitos and I was part of the heal team for them.
I was standing in the midst of about 10 fallen heroes (as our heal team didn't have many flyers for that run) and decided it was time to pull out Howling Twilight to rez them. Our targetter decided to switch to a new target. He must have been using tab to do it and sure enough the tab selected Hami just as I pushed the power button...
The result was a glorious Yellow Dawn. Every single hero went down in the blink of an eye.
I was so new and uninformed that I decided to spend my time trying to get myself and them back up and running.
I hit the debt cap that night. My SG mates felt sorry enough for me that we spent about 3 or 4 hrs street sweeping PI just to trade off my debt.