What if Custer had listened to his Indian scouts, not divided his forces into 3 separate groups who couldn't help each other, and had made a far more judicious and sensible massed attack on the enormous Indian encampment at the Little Big Horn?

(In my opinion, he'd still have probably experienced a reverse and had to retreat eventually...but his people wouldn't have got wiped out the way they did.)

Custer, however, was a man who never hesitated, but always struck without delay, no matter what the odds. It had served him well in previous encounters. It did not serve him well at Little Big Horn.