Find match pattern and delete the first occurrence

To delete first duplicate:

awk -F- 'NR==FNR {++a[$1]; next} a[$1]==1; {a[$1]=1}' file file

Read same file twice. Count $1 on the first read, decide what to do with the count on the next.

another awk

$ awk -F- 'NR==FNR{a[$1]++; next} !(--a[$1])' file{,}

CKLHQD16BWP210H6P51CNODSVT-(.CPN(#),.E(1),.TE(n9),.Q(n10)); |5
LHCSNQD1BWP210H6P51CNODSVT-(.CDN(n10),.D(),.E(1),.SDN(),.Q(n11)); |6
OAI21D8BWP210H6P51CNODSVT-(.A1(n11),.A2(),.B(),.ZN(n12)); |9
DCCKND16BWP210H6P51CNODSVT-(.I(n12),.ZN(n13)); |10
INVSKFD14BWP210H6P51CNODSVT-(.I(n13),.ZN(n14)); |11
NR2SKRD12BWP210H6P51CNODSVT-(.A1(n7),.A2(n1),.ZN(n8)); |2
MUX2D2BWP210H6P51CNODSVT-(.I0(n8),.I1(n2),.S(),.Z(n9)); |4

double scan file, first round count the occurrences of each key, second round print the last one only.

This might work for you (GNU sed):

sed -E 'H;x;s/^(n[^-]*-)[^n]*(.*1)/2/;x;$!d;x;s/.//' file

Make a copy of the current line in the hold space.

If the current key already exists in the hold space, remove the first line.

At the end of the file, swap to the hold space, remove the first newline that was introduced when making copies and print the results.

Could you please try following, written and tested with shown samples in GNU awk.

awk '
BEGIN{ FS="-" }
FNR==NR{
  arr[$1]++
  next
}
arr[$1]>1 && ++arrAgain[$1]==1{ next }
1
' Input_file Input_file

Explanation: Adding detailed explanation for above.

awk '                             ##Starting awk program from here.
BEGIN{ FS="-" }                   ##Setting field separator as dash here.
FNR==NR{                          ##Checking FNR==NR condition which will be TRUE when 1st time Input_file is being read.
  arr[$1]++                       ##Creating array arr with 1st field index and keep increasing its value with 1 on each of its occurrence.
  next                            ##next will skip all further statements from here.
}
arr[$1]>1 && ++arrAgain[$1]==1{   ##Checking if arr value with 1st field index is greater than 1 and its first time occurring in arrAgain then skip that line.
  next                            ##next will skip all further statements from here.
}
1                                 ##1 will print current line.
' Input_file Input_file           ##Mentioning Input_file names here.