The unit’s place digit in $4^{4n}$ is

We can observe,

$4^1=4$

$4^2=16$

$4^3=64$

$4^4=256$

$4^k\forall k\in N$

If $k=Even,4^k$ last digit is always 6

If $k=odd,4^k$ unit’s digit is always 4

Here given $4^{4n}$

$4n$ is clearly even can be written $2\left(2n\right)$

$\therefore$$4^{4n}$ unit’s digit is 6.