Getting Easy

$1! = 1$

$2! = 2$

$3! = 6$

$4! = 24$

$5! = 120$

$6! = 720$

$7!, 8!,$ and forth, will always have $0$ as their unit digit.

The unit digit of $11!$ is $0$

So, the unit digit of $11! - 1$ is $\boxed{9}$

$11! = 11 × 10 × \cdots$
So, since $10$ is one factor of $11!$ , it will always have $0$ in its units digit.
So, when we subtract one, we would obtained some number which has its unit digit $\boxed{9}$ .