The missing character is D, P.
The sequence is a list of letters that are two places apart in the alphabet. The first letter is A, and the second letter is C. The third letter is E, and the fourth letter is G. The fifth letter is I, and the sixth letter is K. The seventh letter is M, and the eighth letter is O. The ninth letter is Q, and the tenth letter is S. The eleventh letter is U, and the twelfth letter is V. The thirteenth letter is X, and the fourteenth letter is Y. The fifteenth letter is Z.
The sixteenth letter in the sequence should be two places after Z, which is P.