After looking across the internet for about an hour, I decided to register an account and ask a question :)
I'd like to remove all lines that don't contain at least one uppercase letter, lowercase letter, number and special symbol [Examples of Special Symbols: !@#$%^&*()] in Notepad++
josukeisbig JOSUKEISBIG JosukeIsBig JosukeIsB1g JosukeIsB1g!
The only related thread I found was this: How to remove lines that not containing any uppercase letters or lowercase letters or numbers notepad++
But OP didn't specify special characters.