Might not be the biggest one time hit but a comeback, a couple years ago I did deposit $2000 on an online casino, lost it all within an hour, literally nothing paid. I managed to get $30 rake back, did 10 autospins on $3 just to rip and go to sleep, but apparently it was meant to be because it triggered a bonus, paid $5k, run those up to $35k within 2 hours and went to bed.
(Lost like 20 k of it in the next couple days but still lol)