Find the missing character?

The missing character is $\boxed{\text{Q}}$.

The other three characters, $\text{A}$, $\text{F}$, and $\text{R}$, are all in the set of letters that appear in the alphabet twice. The letter $\text{Q}$ is the only letter in the alphabet that does not appear twice.

Here is a table showing the number of times each letter appears in the alphabet:

Letter | Number of times it appears in the alphabet
——- | ——–
A | 2
B | 2
C | 2
D | 2
E | 3
F | 2
G | 2
H | 2
I | 3
J | 1
K | 2
L | 2
M | 2
N | 2
O | 2
P | 2
Q | 1
R | 2
S | 2
T | 2
U | 2
V | 2
W | 2
X | 1
Y | 2
Z | 1