Short Answer 
The analysis of the three columns reveals distinct patterns: the first column has non-incremental letters K, P, and I; the second column features a symmetric repetition of the letter N; while the third column is completed by determining the missing letter P, resulting in the final sequences of K N H, P T L, and I N P.
Step 1: Analyze the First Column
In the first column, the letters are K, P, and I. To understand their sequence, observe their positions: K is the 11th letter, P is the 16th letter, and I is the 9th letter of the alphabet. Notably, while there is a change in the alphabetical sequence, it does not follow a clear incremental pattern like the other columns, which is important for further analysis.
Step 2: Examine the Second Column
The second column features the letters N, T, and N. A key observation here is the repetition of the letter N as both the first and third entries. This indicates that the letter remains constant for the first and last positions in this column while the middle letter shifts. This symmetry provides insight into the pattern’s structure across all columns.
Step 3: Determine the Third Column Pattern
The letters in the third column are H, L, and an unknown letter. To find the missing letter, evaluate their alphabetical positions: H is the 8th letter, and L is the 12th letter. By adding 4 to L (12 + 4), we calculate that the next letter is the 16th letter of the alphabet, which is P. Therefore, the complete letter pattern is K N H, P T L, and I N P, confirming that P is the letter that completes this sequence.