2008 Finals, Boston vs. Lakers: In one game the Lakers nearly came back from a 20+-point deficit in the last 8 minutes, and in another game the Cs did come back from a 24-point (I think) deficit in the last 8 minutes.
You got that half right.
In game 2, the Celtics were up 24 points with 8 minutes to go in the 4th quarter. They went on a 31-9 run to close it to 2 with 38.4 seconds left. Paul Pierce and James Posey (man, I miss James Posey!) clinched the game with free throws. If Kobe Bryant and Sasa Vujacic can lead an almost 4th quarter comeback, can't Lebron and whoever?
Meanwhile, in game 4 the Celtics trailed by 24 points in the 3rd quarter. However, they went on a 21-3 run to end the quarter, so by the beginning of the 4th they only trailed by 2. Eddie House (man, I miss Eddie House!) sealed the game. So, it wasn't in the last 8 minutes. But still, they came back from 24 down to win.
In game 5 the Celtics were down 14 in the 4th quarter, and went on a 16-2 run to tie it, but lost the game. Then game 6 Rondo had his amazing 21 points, 8 rebounds, 7 assists, 6 steals game and we won by 39.
In short, bigger comebacks have happened.