您可以使用单个捕获组，然后匹配CON后跟_或字符串结尾：

^(?:[^_\n]*_){9}(CON)(?:_|$)

说明

• ^字符串开头
• (?:[^_\n]*_){9}重复9次，匹配除_或换行符以外的任何字符，然后匹配_
• (CON)捕获组1，匹配CON
• (?:_|$)匹配_或Assert字符串结尾

Regex demo

(?<=              # Match after
  ^               # the beginning of the line, then
  (?:[^_]+_)      #         1+ non-underscore chars followed by '_',
  {9}             # 9 times
)                 # 
CON               # literal 'CON',
(?=_|$)           # followed by '_' or end of line.

试试看on regex101.com。