Find all strings except one string using regex

I want to match all strings except the string "ABC".
Example:

 "A"     --> Match
 "F"     --> Match
 "AABC"  --> Match

 "ABCC"  --> Match
 "CBA"   --> Match
 "ABC"   --> No match

I tried with [^ABC], but it ignores "CBA" (and others).

Answer

^(?!ABC$).*

matches all strings except ABC.