Bullies always do well when they’ve got their gang with them. Generally, no bully is up to a fair fight, but when it’s four, or five, or a hundred to one, they’re suddenly real brave. In fairness to Biff, in Back to the Future, he didn’t hide, which was probably his only positive quality (Thanks to Thomas F. Wilson for a great character).
Cowards, until their back is to the wall, spend their time bragging to everyone about their greatness. Their sycophants fall over one another to; a) praise their boss and; b) jockey for position and stab one another in the back.
Eventually, the bully falls.
Hitler hid in the bunker and committed suicide, leaving what was left of Germany to fend for itself. Osama bin Laden sent others to crash into the Twin Towers while he remained safe. Muammar Gaddafi, hid in drain pipe** until his people dragged him out and killed him. Saddam Hussein the great and powerful hid in a hole in the ground. Cowards, every one of them.
On the other hand, heroes stand up for what they believe, either taking the lead or standing alone. The mark of a hero is that they get as scared as anyone else, they push though their fear and act to do what they believe in. They may fall. They mall faster than cowards, but they fall as heroes.
* With apologies to the Beach Boys
** Nothing against sewer pipes–I live in one, but everybody knows it, so I’m not hiding.